Orthorasterizer: Code clean up

Fix the tabing and bring back in the expand 1 that I dropped
earlier. It is need because we are getting floating point intersection
wrong somewhere.
Core.h: Remove specialized hears from Core.h

The existance of Core.h seems like a bad idea. I was just copying
VW. Misuse of this file just make compilation times longer.
point2dem: Remove block_cache for improvement

Block cache is no longer needed now that OrthoRasterizer has a better
access pattern. We actually do better and have more cache if we don't
use block_cache.
dg_mosaic: Add incorrect image placement check

See if we are trying to insert more than one image to a line location.