Allow tree photos and collection UDFs in search filters

Fixes #1239
Don't query the ecobenefits service if there are no trees.

It's not possible to get correct SQL from an EmptyQuerySet, so if
there are no trees, we shouldn't try.
Show all zeros for ecobenefits with no trees
Fix applying display filters to the DOM

Check "Show trees" and "Show empty planting sites" when "plot" is in the
display filters
If all display filters are checked, don't add anything to the URL
Clean up converting search filters into url

Adds a helper function for getting the query string for a
set of filters
Merge pull request #1255 from maurizi/fix/long-url

Fix search issues
Merge pull request #1251 from maurizi/fix/ecobenefits-search

Fix ecobenefits search
Support "total eco benefits" for plots/trees
Modify searchToBoundary to work on the nested filter object.

Fixes #1254 Search by location polygon not working on development
Re-enable resource counts
Merge pull request #1267 from OpenTreeMap/topic/show-resource-counts

Re-enable resource counts
Merge pull request #1266 from maurizi/fix/location-search

Modify searchToBoundary to work on the nested filter object.
Merge pull request #1256 from OpenTreeMap/topic/show-total-currency

Support "total eco benefits" for plots/trees
Show the correct plot/resource marker on detail page
Support "None" in currencies
Fix lint
For methods added to map, get map using `this` rather than `that._map`

Because `that._map` is null after the first polyline is removed from the map.
When a polyline is removed from the map, remove it from the internal polyline list.
Better cleanup of area polygon.

Fixes OpenTreeMap/otm2-addons#38
Fixes #1265
Fixes #1264