Final game workflow.

- Added a simple game workflow: Title -> Game -> Win -> Title ...
- Added assets for title and win worlds.
- Added fade in/out effects for transitions between levels.
Improved colours.

- Player is now mostly white (some transparency remains althouth I think
  nobody is going to notice).
- Player can look at both directions now.
- Finish line is now of the same colour as the tiles to make more sense.
- Finish line now has an ugly animation that pretended to represent are
  flow but is not doing a terrible job...
- Background is not dark grey to resalt actual colours.