[ConvDiff] Thermal face enhancement

[rubenzorrilla]

At the moment, the Convection-Diffusion application only has Imposed temperature and Heat flux as Conditions. This means that no ambient heat exchange (convection and radiation) can be considered.

Inside Kratos Multiphysics, such behaviour is implemented inside the thermal_face.cpp and requires to retrieve EMISSIVITY, AMBIENT_TEMPERATUREand CONVECTION_COEFFICIENTvalues from the conditions properties. This means that a new property has to be written in the materials.json for each new thermal face that the user selects (these values might change between thermal faces). Besides, it is required to write the submodelpart containing the thermal face mesh data in the .mdpa.

So far, properties-related tree assignations are located in the Partsfolder of the tree (not inside Conditions, which seems to be the proper place). Besides, this new feature will not require a process.

Having all this in mind, it is not so much clear how to proceed... @jginternational suggestions? (thanks in advance)

[jginternational]

My suggestion is to add the parameters to the process, and then, in the python side, handle those parameters

[rubenzorrilla]

Makes sense to me (should be much easier than the GUI implementation).

[rubenzorrilla]

522 already merged.