Changed some solver(preferred) or test tolerances slightly to get tests satisfied on BGR servers

The getActiveElements function of a process is used from
now on (as it is correctly handling multiple variable deactivations)
and with this the process_id and process_variable are no longer
needed as arguments.

This fixes the issue that the assembly is not executed when
the first process' variable is deactivated.

... this should improve the compilation error reporting

Christoph Lehmann authored 9 months ago and Dmitri Naumov committed 9 months ago

... from the local assembler to the interface classe, like in TRM.

With that change "Volumetric"/"Python" source terms can be applied to nodes, as well.
Thereby, the special "Nodal" source term has become obsolete, now.

of the function to comput B_dil_bar matrix, and some other minor changes

... from assembleWithJacobian() into a separate method.
I added some constitutive data structs and reused some from TRM.