Request to extend modeling guideline

[MarcBehrens]

@UweSteinkeFromSiemens during verification of the architecture some principles whic are used came up.

this is the request to document the principles inside the modeling rules https://github.com/openETCS/modeling/tree/master/ModelingRules

• each folder itself beneath https://github.com/openETCS/modeling/tree/master/model/Scade should contain only one *.etp file
• within each *etp file only one high level architecture function according to https://github.com/openETCS/modeling/tree/master/openETCS%20ArchitectureAndDesign is contained

related to openETCS/validation#277

@BerndHekele @mahlmann @AbdelnasirMohamed

[UweSteinkeFromSiemens]

No further action required during the remaining duration of the openETCS project.