Delete GL Groups object

Per today's sync, GL groups object is likely not necessary. Need to:

1. Delete from models.py
2. Update Project attributes to remove GlGroups FK
3. Update Project save definition to remove GLGroup related logic
4. Update Project.short_name_with_namespace field so that it no longer calls GLGroups
5. Check all templates for any references to GLGroup object or methods
6. Run all tests and fix any broken tests.