Add stuff to the public API

[sgdc3]

Since we use injection developers are unable to hook into out code except the API, we need to provide some new methods like getRegisteredPlayers()

[sgdc3]

@ljacqu This still need unit test, could you take a quick look when you're back? :)

[ljacqu]

@sgdc3 Done—thanks for the hint 😉

[sgdc3]

Ok, forgot to close this ;)