added OL to search
added UI for search by extent
UI cleanup for extent search
added extent filter to search results page
removed extra openlayers in favor of OL wrapped in ExtGeo
added geoexplorer JS packages in search templates and wrapped in Ext
Merge branch 'searchmap' of https://github.com/nathanhilbert/geonode into nathanhilbert-searchmap
Added Nathan Hilbert to AUTHORS

He contributed extent based search.
Fix spelling error and remove duplicate entry in AUTHORS.