Improved SourceTests, again

Fixed:
- If run locally, BlockCharcacterTest and LicenseTest failed files in 'build' folder (changed Utils.accept)
- BlockCharcacterTest also failed on strings.xml and UiTestUtils --> ignored

Improved:
- If we only check .java files, lets only check files in /src folders.
- Add LegoNXTBTTests to some Tests.
- error messages, (Path instead of FileName) and one was just plain wrong
- All Directory Arrays are defined in the Utils class, to reuse and only have one place to change things (for example if a subteam adds a directory)