Update var declaration

- change name to dataManager
- move layertype out of dataManager
(otherwise throws error when using in same declaration)
Formatting
Remove map layers - these should be dealt with in browse.js

I took these out of there because I think dataManager should only
manage the data used in the layers, not the layers themselves or
the map since the map logic seems somewhat separate from the data
loading logic and should be broken out into browse.js
Remove changes to layers from locationUpdate function, use dataManager
Remove helper function

The helper function was necessary only because we thought the dataManager
object was going to be messing with the map layers; however, in the hopes
of changing as little code as necessary in browse.js I think we want to
keep that stuff in there
Remove zoomListener - that will be handled in browse.js

Rename filterListener to onFilterChange -- more accurate
Formatting/Remove geojson from neighborhoods initially