Neighbornews add/edit form: Better feedback when clicking map

[slinkp]

Currently on the neighbornews add/edit form, when you click the map, it uses that point and discards anything in the address field. The server will reverse-geocode after you submit and populate the address, but the user can't tell that without submitting, so it's confusing - hard to know what you're doing. The address field does update the map, but only when you click the "Map it" button.

Fixcity had a pretty slick UI for this, updating automatically as you left the address field; reverse-geocoding via ajax and updating address if you clicked the map; and avoiding things getting out of whack if you submitted the form before ajax requests completed, ensuring that whichever one you touched last was used.
We could re-use that code. But we don't have an exposed API for reverse-geocoding, would need that first.

[slinkp]

(In [dbf65e1]) Somewhat better UI for neighbornews map / address inputs.
Still doesn't reverse-geocode, so clicking the map is not ideal,
but it now removes the stale address. Refs #284.

[slinkp]

Ticket imported from Trac:
http://developer.openblockproject.org/ticket/284
Reported by: slinkp