Functionnal Registration step done

The registration step isn't complete (edit known players, remove players), but is working enough to play its role: to have players in it.
TODO:
Starting view:
- defensive programming
- compatibility with the import/export tdf incoming
Registration view:
- edit player (known or registered)
- remove player (known or registered)
- defensive programming
- compatibility with the import/export tdf incoming

Moving out to Recap view:
- offer choice of pairing system
- offer options on said choice
- calculate number of rounds played
- go to next step - starting the tournament
update todolist