The next cleaned up version of Kothic-JS

An attempt at cleaning up all unnecessary cruft in Kothic, leaving only barebones rendering code, and another pass at heavy performance optimization.

### TODO

#### Performance

 * [x] Fix lots of false negatives on same-style rendering check because of checking against next feature that can be outside of "renderable" condition (25-35% faster geometry rendering!)
 * [x] Sort styled features by fill/stroke-color to minimize stroke/fill
 * [x] Replace the old RTree with RBush, my new high-perf R-Tree implementation (20% faster rendering)
 * [x] Fix excessive getWidth calls in textOnPath, approximate  (40-50% faster label rendering)
 * [ ] Fix caching the same styles with different names as different cache entries
 * [ ] Render polygon fills in two passes (color, then image) for less fill operations
 * [ ] Try implementing lazy async rendering in batches <16ms for 60fps (or <32ms for 30fps)

#### Styling

 * [ ] Move everything MapCSS-related like styles, python scripts and a `kothic-js-mapcss` adapter into a seperate repo _(in progress)_
 * [ ] Refactor Kothic styling mechanism to accept more generic (non-MapCSS-specific) style implementations

#### Other

 * [x] Remove unnecessary crap like unused or easy-to-avoid utility functions, debugging placeholders in code etc.
 * [x] Clean up JS code of archaic constructions and overengineering