Terrain2

Improvements:
 - Consistent triangle alignment, fixing the crack noticed in http://bugs.openmw.org/issues/274 . Note that alignment is still not the same as vanilla. Vanilla uses a weird diagonal pattern. I hope there aren't more trouble spots that will force us to replicate this, but at least we can do that now.
 - Fixes several blending issues and cell border seams
 - Fix map render to use the terrain bounding box instead of an arbitrary height
 - Different LODs are now properly connected instead of using skirts
 - Support self shadowing
 - Normals and colors are stored in the vertices instead of a texture; this enables per-vertex lighting which should improve performance, fix rare compatibility issues due to the PS getting too large and mimic vanilla better
 - Support a multipass fixed function fallback (though the splatting shader usually performs better)
 - Designed for distant land support - test: https://www.youtube.com/watch?v=2wnd9EuPJIY - we can't really enable this yet due to depth precision issues when using a large view distance