Cleanup tasks of com.mbeddr.mpsutil.ecore

[alexanderpann]

Some tasks that I noticed when we clean up the language a bit more:

• MPSModuleRepository.getInstance() should be replaced by model.getRepository() in the generator.
• remove System.out.println statements and replace by log statements
• fix stuff where it says hack or TODO
• rework colors like for the assert-instance-import-export statement
• classInterface test model is empty
• com.mbeddr.mpsutil.ecoretransofmation.sandbox: EcoreFIleINfo points to invalid location
• Tests: generated interfaces and concepts should be in own language in structure aspect instead of a solution to avoid model check errors