[Tournament] Huge refactor : tournament inscription generalization (manual mode)

DONE :
- We can now register to several tournament with one user
- We can register as a simple player or as a team, depending tournament parameters
- Manual mode (no API validation) works, like lol tournament type

TODO :
- DATABASE MIGRATION IS HAZARDOUS AND NOT YET READY. Don't push this commit on prod!
- Check for LoL username validation. I've probably broken validation services
- List of validated and pending teams is broken (my account page)
- Tests