Convert track from Rfactor

[joevenzon]

but i've always been a fan of the level editor being the same executable as the game engine.

Me too (now).

The current track-editor doesn't share code with the game. This means one has to replicate/update functionality which sucks big time.

The track editor shares code with a really old version of the game. There's not really much code that's specific to the track editor, just some line drawing and mapping of input buttons to TRACK::function calls.