Fix bug when a players cannot connect to the rest of the players.
- In such case, server will intermediate as broadcaster between this players and the rest. Not the best way but that's how the client works, we cannot do much about it.
- Added udp game message ids.
- Added ChannelFuture getter to NettyUdpServer.
- Added NettyUdpServer getter to the main class.
- Added body getter to ClientMessage.