Disconnect Player from Car implemented.

- after game over (Client has to send PlayerMessage.DISCONNECT)
notice: otherwise client has to send PlayerMessage.SET_READY to announce readiness for next game round
- on network connection abort (client-server) and timeout exceeded (currently 15 seconds) Car is also disconnected from Player
notices:
-> should work at any time
-> No matter what caused the disconnect - Car will be available again to all Players after timeout exceeded (free cars message)
-> Client can try reconnect within the timeout and send  PlayerMessage.RECONNECT_REQUEST to abort timeout and stay connected to the Car

Implemented and tested with plr-simulator/server implementation.