Geocoder module: Show marker / bbox for selected entry

[chrismayer]

Show a marker (for point based geometries) or a bbox (if available) for the selected entry in the result list of the Geocoder module on the map. If the geometries are shown should be optional and thus a config option should be introduced.

See #29: For the general concept of the Geocoder module and #95 for the current implementation and its discussion.

[justb4]

Ok, have done something like this in the past:

It has both a marker and balloon text, possibly a too broad solution? The issue is always if the marker/bbox should be sticky, or how to clear these. Best start with simplest solution.