[CMDMANAGER] implemented !cmdgrant and !cmdrevoke

This implements #215 + a minor fix to the iourt42 parser (FreezeTag gametype declaration). The change is so small that I don't want to create a separate pull request for it (unless you think it's necessary).

@thomasleveil I didn't tested it live yet, but test cases are passing. Anyway, a little review would be appreciated :smile: