[develop] Performance Improvements (Markers, MarkerClusterer Rewrite)

Performance tweaks

- lazyUpdate map.coffee
- modelsByRef to disable equality checks
- marker managers improvements (MarkerClustererPlus dropped from google tools sdk)

This is to open up this major PR for discussion how to handle merging in these changes.
Removing async code needs to be debated. As stated (by @ccg1415 ) the synchronous improvement to MarkerManager and MarkerClusterer and ClustererMarkerManager are significant enough that async code may not be needed.