Server Communication (Python Interface) pre and post timestep

Third version of the server communication feature.

Updates:

The communication now happens before and after each OGS calculation. The name convetions has been adjusted, so that the communication "pre" and "post" can be recongnized more clearly. The name conventions of the test cases has been made more generally, because the feature is not restricted to SimulationX, but is actually just a python interface feature.

Issues:

• For building purposes I still have to edit the Dependencies.cmake file, otherwise some options would not be enabled during the cmake build process.
• I'm not sure whether test case "3D_3BHEs_array_python_interface" can be run. A prerequisite is to run it with TESPy 0.3.2, but I was not able to install the package, because apparently there is no such version? If this leads to troubles, this test case could also be deleted, because test case "3D_Beier_sandbox_python_interface" already shows the functionalities.

Feature description:

Basically it is used to communicate with a python script, which is defined in the .prj-file. Additionally you have to insert a switch <use_server_communication>true</use_server_communication>. For details please be refered to the test case T\3D_Beier_sandbox_python_interface.

In general, this feature can be used as a data transfer to python before and after each OGS calculation. The range of use cases is greater than only our use case.

Our specific use case is a server communication between Modelica (SimulationX) and OpenGeoSys. The data transfer is defined as: preTimestep: Modelica sends updated T_in and flowrate to python script postTimestep: OGS sends t, dt, T_in, T_out and flowrate to python script In the python script the transfered data is handled specifically, so that each software gets the data which is needed.

1. Feature description was added to the changelog
2. Tests covering your feature were added?
3. Any new feature or behavior change was documented?