Rip out broken display filter code
Change client-side to handle display filters as a special case

Advanced search display filters are now separated from the filter
object syntax. Instead there is a simple list of what to show.
Use classproperty for map_feature_type and display_name
Change advanced search display filters
Use display filters in eco benefits search
Add display filters to exporter
Merge pull request #1230 from maurizi/fix/display-filters

Fix display filters