use same one-entry-queue strategy from Scene.rebuildGeoemtry() for scene definition updates, Scene.updateStyles()
rename/consolidate some scene config methods
fix cases where child render modes were overwriting properties of parent modes
Merge branch 'master' into mode_refresh_queue
Merge pull request #48 from tangrams/mode_refresh_queue

Use throttle-with-single-entry-queue strategy for re-parsing styles & re-compiling GL programs