move sprite class to map directory
break out StyleSource from Source, move getActiveSources and
updateSources into Map::Map, move getAccessToken from Style to Map

Conflicts:
	include/llmr/style/style.hpp
	src/map/source.cpp
	src/style/style_layer.cpp
	src/style/style_parser.cpp
Merge branch 'master' into stylesource
Merge branch 'master' into stylesource
Merge branch 'master' into stylesource
add forward-declared Source shared_ptr to style_bucket
Merge branch 'master' into stylesource
Merge pull request #362 from mapbox/stylesource

Break out StyleSource struct