speedquest

[morganherlocker]

This ticket is a master ticket capturing several improvements focused around making tile-cover fast with lines and polygons.

• [x] scanline algorithm
• [ ] Active Edge Table scanline index
• [x] bresenham's line algorithm
• [x] bbox low zoom optimization
• [x] broad tests

cc @yhahn @ingalls @sbma44 @karenzshea

[morganherlocker]

Punt on AET for now, since it is map-reducable