Add Google Map Geocoding Interface

This pull request closes issue #163. 

It removes the openlayers widget for geocoding and adds a google maps interface for geocoding.

By default, the geocoding uses the address entered into the form. If unsuccessful a help message appears detailing how to manually add a point by right-clicking.

If multiple results appear from geocoding another help message appears letting the user know they can manually select the correct marker by clicking on it.