Added DebugGrid().
Has a bunch of static crap in GenerateTerrain() for debugging purposes.
generator.cpp: %4 -> %2  fixed the polygon selection issue.
game.cpp: fixed ordering of terrain chunk rendering to match the way the chunks are stored in Terrain.
game.cpp: in terrain rendering, divided chunk_size by 2 for stepping the position/offset.  Don't know why this is necessary but it is to avoid gaps.
Removed cruft and commented code that had been used over the course of debugging generator.cpp
Added Terrain loading based on position and direction vectors.