Consistent base maps

This PR modifies all the leaflet mapping applications so that they have a base map menu that is consistent with the base maps shipped with GeoExplorer
If BING_KEY is unconditionally defined here, all the cascade of definitions works and the javascripts check with try catch never except, if your purpose is disable Bing maps removing the 'bing_key' attribute maybe a comment above line 69 could clarify the concept.