Structural Mechanics small enhancements in solver

[philbucher]

4 small enhancements:

1. The user can define auxiliary Variables that are to be added to the ModelPart, no need for doing that manually any more. Especially after the issues in GiDIO segfaults without Variables added #492 . @KratosMultiphysics/fluid-dynamics this might be interesting for you too
2. Replaced Model{} by Kratos::Model
3. Removed an unnecessary if (bodies_list is always there since it is in the defaults)
4. Using VariableUtils().AddDof in the tests

[loumalouomega]

Thanks

[philbucher]

@loumalouomega is there a need for the bodies_list?
It seems like this is copied from the fluid stuff, it is not used anywhere
I think problem_domain_sub_model_part_list does the same

Can we remove it? (Maybe first with a warning that it is deprecated and will be removed soon)

[loumalouomega]

No, and in principle, thanks to the Model class we don't need this any more, this was the things I was meaning when I said that we could simplify the parameters thanks to the Model

[philbucher]

But problem_domain_sub_model_part_list and processes_sub_model_part_list we still need, for the computation of the computing_model_part, right?

Can we remove sth else?

[loumalouomega]

Normally these submodelparts are defined in the mdpa and can be acceded with the Model, i would need to do some tests to check it

[philbucher]

I know that they are there, but we do not necessarily want to define the computing_model_part with all the SubModelParts that are present in the MainModelPart

Therefore I think it should stay as it is

[loumalouomega]

Therefore we need to open a discussion with the whole @KratosMultiphysics/structural-mechanics

[philbucher]

ok I will make an issue for that and add a warning abt the bodies_list