Resolve issue with dependancies between Controller and Datamodels

[simontaurus]

e. g. WikiFileController needs WikiFile, which is not loaded/installed by default. That why model schemas currently need to be loaded first, then the Controller class is imported (which violates PEP standards)

Solutions:

• Add required data models for core functions to model.entity.py or model.static.py
• Inform users about potential outdated models
• Fetch model schemas automatically before running the import of a Controller, e.g. through the init.py of the controller model