add halftone shader
add halftone shader option to demo
add support for booleans in JS->GLSL uniform translation
use boolean uniform for halftone color switcher
Merge branch 'master' into decanvas

Conflicts:
	dist/vector-map-worker.min.js
	dist/vector-map.debug.js
	dist/vector-map.min.js
	src/gl/gl_renderer.js