(closes#3663)
* Add Nuclear Explosion Site and Military Office presets
* Add Bunker Type field
* Improve styling rules for preset icons
* Improve search terms for all military presets
* Nest military presets under `landuse=military`
* Add ref, iata, icao fields to Military Airfield
* Don't set area pattern fills on buildings
This includes some renames for clarity.. "surface" -> "selection"
to make it clearer that rendering functions take a selection, and
don't necessarily render to the literal `#surface` node anymore.