squashed stylequest merge

* uses OSM Bright style
 * adds dot shader
 * adds layer translation
 * adds dashed line support
 * adds style array parsing
 * improves background layer parsing
 * improves style constant parsing
 * fixes sprite JSON pixel ratio parsing

src/platform/platform.cpp

@@ -1,3 +1,3 @@
 #include <llmr/platform/platform.hpp>
 
-const char *llmr::kSpriteURL = "http://mapbox-kkaefer.s3.amazonaws.com/static/sprite";
+const char *llmr::kSpriteURL = "http://mapbox-kkaefer.s3.amazonaws.com/static/osm-bright-gl/sprite";