Brakelights effect, shadow layer and other improvements.

- Added customizable brakelights effect.
- Added customizable shadow sprite layer.
- Added capability to parse relative file paths.
- Added new property 'sprite_frame_count', which allows one to specify
sprite frame count for all states (instead of a per-state basis).
- Allowing multiple def's per subfolder.
- Added option to specify course music.
- Display kph instead of km/h.
- Rounding up dial tachometer max rpm to nearest thousand.
- Improved performance of courses drawing, specially ones containing
sprites.
- WIP course editor state.
- Updated fgeal submodule version to 0.7.2
- A lot of refactoring.
- Fixed lap info display offset.
- Fixed background parallax.
- Other fixes.