Bugfix: Model loading not using all textures.
Big commit:

- Refactoring the whole main code introducing the Game class along the way
- SpaceObject collision with player now is executed in an own method
- Added a targeting flag for the SpaceObjects to mark which can be targetted by the player
- Introducing a new speed control class Speed which handles accelerations for smooth controls
- Added four power ups, where two are being used at the moment: speed and time
- Adding a speed element to the HUD
- Forgot to add the distance.svg during a recent commit