updates for v0.2 alpha

Bugs:

• Allow M2M TTConstraint not to be saved before enriching models
• Right authentication error code
• Regeneration infos in fetch_week_infos (not in the cache any more)
• Ghost course
• Bknews shift

Features:

• 3rd digit of rights allows changes despite future generation
• Different levels in room selection:
  1. Available rooms of same type
  2. Available rooms
  3. All rooms
• More fields (all required) in user creation forms