Game loop improvements

[sourencho]

[0a2be30] Split game loop into preUpdate, update, postUpdate

[84a9c60] Create GameObjectController

• The GameObjectController is in charge of updating all game objects and extracting/applying game state from/to them. It owns Player/Group/Mine controllers.
• GameObjectController communicates with NetworkingServer/Client via events.

[e85d352] Disable ClientGameController test

• ClientGameController needs a window to run and travis-ci's tests fail because it can't open a window
• Add todos for issues
• Spawn mines

[3040f39] Minor cleanup