Creates API for managing OL maps outside of Aperture

**WIP: Do not merge yet**

Previously if you wanted to use Aperture visualizations over a map you had to create and manage the map itself (including TMS, WMS, etc map layers) using the Aperture-wrapped aperture.geo.Map vizlet. This PR adds new APIs (eventually old ones will be deprecated and removed) that allow the creation of the map, the base layers and other layers to be managed exclusively using OpenLayers' own APIs. Aperture map-based visualizations can be added by creating a `OL2MapLayer` (a top-level layer, cannot be added to other Aperture layers) and adding it's member `olLayer` to the OpenLayers map.

Other changes that were part of making this happen:
 - Removed ESRI map implementation
 - Unwrapped creation of map APIs upon configuration that was added for ESRI support. Not needed regardless, easier and cleaner to check for existence of OpenLayers on the window
 - Fixed vizlet creation code to accept a spec object that includes an actual DOM element (not just id)
 - Fixed `MapNodeLayer` (and new derived `OL2MapLayer`) to leave width/height alone, setting to size of the entire world in pixels is not (yet) necessary and bloats code

To Do:
 - Break KML/GeoJSON rendering support out as did with MapNode