add a simple location and community search control

[ghost]

Add a control to the map that allows the user to type a location, part of a location, or the partial name of a community - geocode the address provided (or use the location of a named community) and then zoom/pan to that location on the map.

NB. Google offer autocomplete as a part of their APIs - and this might make a good addition to the control. There are plenty of examples of this used with their geocoding APIs to help users select a real location to geocode.

NNB. If it's not trivial to combine addresses and communities in the same autocomplete, just do one or the other, and we can compose a control that allows the user to select between the two options.