Add support for thermo-mechanical problem

[Rombur]

This PR does the following:

• rename Physics to ThermalPhysicsInterface: I don't think we need Physics as a base class for the thermal and the mechanical physics but the class is still useful because it reduces the number of template parameters we need in adamantine.hh. We could do without but I think it would make the code harder to read
• rework adamantine.hh to get ready to solve mechanical problems
• rework the inputs, update the README and the database validation
• add mechanical physics to adamantine.hh

This needs more testing but we can do it later.

[Rombur]

Updated

[Rombur]

Ooops the CI didn't pass. I don't know why the result was not reported back.