Player/LocalPlayer/RemotePlayer inheritance cleanup (part 2 on X)

Player/LocalPlayer/RemotePlayer inheritance cleanup (part 2 on X)

* Server/Client Environments now have an helper to cast Player object in the right type to use it
* Server: use RemotePlayer everywhere and remove previous added casts
* Client: use LocalPlayer where needed
* Environment: remove unused functions (getPlayers(), getRandomConnectedPlayer(), getNearestConnectedPlayer())