[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.
I would create a repo for this as well and assign your own version number. Then we can get rid of our markercluster extensions.