Added milestone module, cleanup, fixed model relationships, ...

- Removed unneeded gitkeep by the Filters core directory
- Updated Milestone migrations
- Added Milestone models, seeders, controllers, repository.
- Added MilestoneEra models, seeders, controllers, repository
- Registered milestone* modules
- Added services, controllers
- Updated university-profile.milestone state
- Fixed missing relationships; added namespaces to relationship of models.