New group model for all newly created groups:
- No more message boxes, requests now integrated into groups and new pages
- The 'public profile' option of private groups is changeable
- The 'anyone can join' option of public groups is changeable
- Better handling for groups with many (thousands of) members
- Resolved lots of small issues regardings groups
- Old groups will be converted later, when we see that the new model is stable

Other:
- Invitation mails less likely to be classified as spam
- better commandline client (auto completion)
- Smaller issues