Fixed CSS problem with popup tip

The little triangle underneath the popup was looking weird.  Turns out
it was mostly because of some of the leaflet_ie.css stuff, so we made
sure that the non-IE CSS took precedence, and wrote in a little override
for an unwanted border as well.
Reinstate Geocoder lookup

Direct Nominatim lookups were playing badly with "nearby" method in
testing. The slowness is largely fixed in the HEAD revision of Geocoder.
Set User-Agent in Geocoder requests; delete custom nominatim lib.

Nominatim-the-service's license requires that we identify ourselves.
The custom nominatim lib is no longer required since Geocoder is now
Fast Enough.
Improve readability of controllers/places slightly.