Multi-material restart for THM process

Adding integration point output for the solid material's internal state variables in the ThermoHydroMechanics process. This required similar steps as have been done before for the same functionality in the SmallDeformation process. Now, also for THM the user can work with multiple materials each containing different internal state variables. A restart from any produced output of some initial simulation is possible, as the entire thermodynamic state is transferred.

Note that the state variable output has to be defined in the prj-file, as well as using the previous output as the mesh for the restart simulation. Initial primary fields have to specified as initial condition.