suggestion to add Swiss-system tournament/cup system

[h3oCharles]

https://en.wikipedia.org/wiki/Swiss-system_tournament
https://en.wikipedia.org/wiki/Swiss-system_tournament#Esports

some motivations include:
- being able to force schedule a match between only two players, and not an entire group at once
- being able to schedule all matches in one cup at once, similarly to how tournaments go nowadays