[Doc] added docu for convergence criteria

Documentation/ProjectFile/process/convergence_criterion/DeltaX/c_DeltaX.md

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+Sets up a convergence criterion that checks only the norm of the solution update
+from one iteration to another.
+
+A relative and/or absolute tolerance value can be specified, which is applied to
+the norm of the whole solution vector, i.e., the entirety of all process
+variables.
+
+At least one of the relative or absolute tolerance has to be met in order to
+satisfy this convergence criterion.

Documentation/ProjectFile/process/convergence_criterion/DeltaX/t_abstol.md

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+The absolute tolerance being applied to the norm of the whole solution vector.

Documentation/ProjectFile/process/convergence_criterion/DeltaX/t_norm_type.md

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+The type of norm of the solution vector being computed.
+
+Possible values:
+
+ - <tt>NORM1</tt> for the \f$l_1\f$-norm
+ - <tt>NORM2</tt> for the \f$l_2\f$-norm
+ - <tt>INFINITY_N</tt> for the \f$l_\infty\f$-norm.

Documentation/ProjectFile/process/convergence_criterion/DeltaX/t_reltol.md

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+The relative tolerance being applied to the norm of the whole solution vector.
+
+The relative error \f$e\f$ is computed as
+\f[e = \frac{||\Delta x||}{||x||+\epsilon},\f]
+where \f$\Delta x\f$ and \f$x\f$ are the current solution update and the
+new solution from the current iteration, respectively, and \f$\epsilon\f$ is the
+machine epsilon guaranteeing that the denominator is always nonzero.

Documentation/ProjectFile/process/convergence_criterion/PerComponentDeltaX/c_PerComponentDeltaX.md

-\ogs_missing_documentation
+Sets up a convergence criterion that checks only the norm of the solution update
+from one iteration to another.
+
+Relative and/or absolute tolerance values can be specified, which are applied to
+the norm of each component (i.e., each process variable, and, if there is a
+vectorial process variable, to each vector component) of the solution vector
+individually.
+
+For each component at least one of the relative or absolute tolerance has to be
+met in order to satisfy this convergence criterion.

Documentation/ProjectFile/process/convergence_criterion/PerComponentDeltaX/t_abstols.md

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+Absolute tolerance values being applied.
+
+In this list of values there must be one value for each process variable (and if
+there are vectorial process variables, for each vector component of that process
+variable). The order of values must match the order of process variables as
+defined by the specific process.
+
+If for a certain component no absolute tolerance shall be applied, zero can be
+given as the respective tolerance value.

Documentation/ProjectFile/process/convergence_criterion/PerComponentDeltaX/t_norm_type.md

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+The type of norm of the solution vector being computed.
+
+See \ref ogs_file_param__process__convergence_criterion__DeltaX__norm_type.

Documentation/ProjectFile/process/convergence_criterion/PerComponentDeltaX/t_reltols.md

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+Relative tolerance values being applied.
+
+In this list of values there must be one value for each process variable (and if
+there are vectorial process variables, for each vector component of that process
+variable). The order of values must match the order of process variables as
+defined by the specific process.
+
+If for a certain component no relative tolerance shall be applied, zero can be
+given as the respective tolerance value.
+
+For the computation of the relative error for each component, see \ref
+ogs_file_param__process__convergence_criterion__DeltaX__reltol.

Documentation/ProjectFile/process/convergence_criterion/PerComponentResidual/c_PerComponentResidual.md

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+Sets up a convergence criterion that checks only the norm of the residuum
+vector.
+
+Relative and/or absolute tolerance values can be specified, which are applied to
+the norm of each component (i.e., each process variable, and, if there is a
+vectorial process variable, to each vector component) of the residuum vector
+individually.
+
+For each component at least one of the relative or absolute tolerance has to be
+met in order to satisfy this convergence criterion.

Documentation/ProjectFile/process/convergence_criterion/PerComponentResidual/t_abstols.md

-\ogs_missing_documentation
+Absolute tolerance values being applied.
+
+In this list of values there must be one value for each process variable (and if
+there are vectorial process variables, for each vector component of that process
+variable). The order of values must match the order of process variables as
+defined by the specific process.
+
+If for a certain component no absolute tolerance shall be applied, zero can be
+given as the respective tolerance value.

Documentation/ProjectFile/process/convergence_criterion/PerComponentResidual/t_norm_type.md

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+The type of norm of the solution vector being computed.
+
+See also \ref ogs_file_param__process__convergence_criterion__DeltaX__norm_type.

Documentation/ProjectFile/process/convergence_criterion/PerComponentResidual/t_reltols.md

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+Relative tolerance values being applied.
+
+In this list of values there must be one value for each process variable (and if
+there are vectorial process variables, for each vector component of that process
+variable). The order of values must match the order of process variables as
+defined by the specific process.
+
+If for a certain component no relative tolerance shall be applied, zero can be
+given as the respective tolerance value.
+
+For the computation of the relative error for each component, see \ref
+ogs_file_param__process__convergence_criterion__Residual__reltol.

Documentation/ProjectFile/process/convergence_criterion/Residual/c_Residual.md

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+Sets up a convergence criterion that checks only the norm of the residuum
+vector.
+
+A relative and/or absolute tolerance value can be specified, which is applied to
+the norm of the whole residuum vector.
+
+At least one of the relative or absolute tolerance has to be met in order to
+satisfy this convergence criterion.

Documentation/ProjectFile/process/convergence_criterion/Residual/t_abstol.md

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+The absolute tolerance being applied to the norm of the whole residuum vector.

Documentation/ProjectFile/process/convergence_criterion/Residual/t_norm_type.md

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+The type of norm of the solution vector being computed.
+
+See also \ref ogs_file_param__process__convergence_criterion__DeltaX__norm_type.

Documentation/ProjectFile/process/convergence_criterion/Residual/t_reltol.md

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+The relative tolerance being applied to the norm of the whole residuum vector.
+
+The relative error \f$e\f$ is computed as
+\f[e = \frac{||r||}{||r_0||+\epsilon},\f]
+where \f$r\f$ and \f$r_0\f$ are the residuum and the residuum from computed in
+the first iteration, respectively, and \f$\epsilon\f$ is the machine epsilon
+guaranteeing that the denominator is always nonzero.

Documentation/ProjectFile/process/convergence_criterion/i_convergence_criterion.md

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+Defines the convergence criterion used by the nonlinear solver solving this
+process.

Documentation/ProjectFile/process/convergence_criterion/t_type.md

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+Defines the type of the convergence criterion.