Portal map search:
  - provide 'loading' indicator while waiting for AJAX (filter) response
    to come back (#search_loading)
  - added notices for map search when number of documents != number of results,
    or when no search (query terms, spatial details) data has been provided
    (#search_notice, .info|.warning)

All UI elements are very basic, and not intended as a final cut. The
functionality is good though.

(This commit is a bit messy; includes whitespace changes. I blame my lack of
patience and a laggy VPN connection)
Portal search layout: only inject available fields into the record
holding container. Map view only provides an ID and spatial coverage,
so don't try to plonk a description or title in there!