Lots of miscellaneous changes and fixes before the site goes live

- Updated the Requirements to include gitolite
- Switched the default database to PostgreSQL
- Student forks are now done after the group is saved
- Student fork upstream merge checker now working
- Student repositories now expect use the same name as the course
- Fixed gitolite call with GL_USER set
- Added check for master branch before resetting
- Better output if LOCAL_CODE is missing in `.gitolite.rc`
- Restricted logging to django_gitolite and courses