Ensure compatibility with different program versions

[jnettels]

Track the compatibility of the different models with different versions of OpenModelica and Dymola.

"FMU" means: The functional mockup unit can be created by that program version and works with pyfmi

Reflects status at b01a639

Model	OpenModelica 1.16.2	OpenModelica 1.18.0	Dymola 2021
Gesamt_Sim_noLP	☑	☑	☑
Gesamt_Sim_noLP (FMU)	not tested	not tested	not tested
Gesamt_Sim_ExcelReadIn	☐	☐	☐ (crashes at 5.7s)
Gesamt_Sim_ExcelReadIn (FMU)	not tested	not tested	not tested
FMU_PhyModel	☑	☑	☑
FMU_PhyModel (FMU)	☐	☐	not tested
FMU_PhyModel_sorted	☑	☑	☑
FMU_PhyModel_sorted (FMU)	☐	☐	not tested
ElectrolysisSystem	☑	☐	☑
ElectrolysisSystem (FMU)	☑	☐	not tested