LIB: 1. Use Protocol::Id for player id instead Protocol::Byte.
2. Implement SignupPlayer  processing.
DEMO: Implement SignupPlayerRequest access.
LIB: Fix id skipping.
LIB: Set client's player id on SignupPlayerResponse.
DEMO: Process SignupPlayerResponse.
LIB: Implement ResignPlayer request, response and notify.
DEMO: Implement resigning player.
DEMO: Add button for take control on player.
LIB: Implement TakePlayer request and response.
DEMO: Implement take control on player.