Master server integration for lobbies

[TheJJ]

After multiplayer games are working, we want to mediate players between lobbies.

• Anybody can host a game
• The game can be chosen to be registered at the master server
• Others can join the game either directly or via master server
• Games can be password or token protected

The masterserver is already implemented but needs to be further polished.

Mainly, openage now needs to implement the counterpart for the lobby stuff.