UBIF-0029 Editable polygon drawing on the map

[glenpierce]

It's trivial to make a given polygon editable in the Google Maps API, the issue is that we need to set it such that our data responds appropriately to those edits. Also, we need to discuss how that might affect users in the long-term before allowing it since it's very possible that this could cause them to get into a situation where they are accidentally creating invalid data.