Feature player (re)spawn

[Taeir]

Players now spawn at the correct position in a map! We even support multiple player positions in a room/level, one will be chosen randomly based on the seed!

• Entities are now part of the level, and not of the game
• Added NoControl, an EntityControl that does nothing (for dummy player).
• VRPlayer.loadEntity now returns a dummy player.
• Added EntityParser.getPlayerSpawnLocation. It removes all players from the entities, selects one player from these randomly, and returns it's position. This allows us to use the dummy players for positioning.
• Fixed corresponding tests
• Changed TestUtil.mockGame to properly create a 1x1 level and a dummy player.
• There is now a LevelFactory for creating levels from single rooms, RoomLevelFactory.

This closes #377.

Better one player on land than ten players in the void

[Geweldig]

Looks good, can be merged in my opinion.

[ChielBruin]

Looks good (and way cleaner). I will merge it