Add event listeners for the additional POI toggles
Added endpoint for geojson searches
Specify additional collections for each toggle
setCollection allows additionalCollections

We listen to events from these collections and show/hide them when
toggled
POICollection handle toggling collection / geojson responses
Added leaflet.markercluster to group icons

 - Used for additional collections (bus, car park, cycle parking)
Add markercluster to require.config
Removed debug logging
Added MarkerClusters to display the additional collections
getIcon function for clustered POIs
Added marker urls/sizes to additional POIs
Refactored the POIs collection to create AdditionalPOICollection

 - To be used for POIs we don't want models for
 - Currently GeoJSON objects
Refactored additionalPOIs config into the config file
Include AdditionalPOICollection
Merge pull request #7 from ox-it/toggle-additional-pois

Toggle additional points of interest