[develop] Performance Improvements (Markers, MarkerClusterer Rewrite)

Performance tweaks via @ccg1415 and [Realmassive.com](https://www.realmassive.com/search/Austin+TX/Office)

You can see how much faster things are there for yourself.

- 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.


Awesome work here. :+1: