Upgrade from the deprecated django-ext-hstore to django-hstore

Allows for easy lookup of hstore members using the same syntax as
normal Django ORM usage.
Add support for UDF collection searches
Merge pull request #1303 from maurizi/stewardship-search-backend

Stewardship search backend
Fix broken reference in migration

djorm -> django
Factor out datepicker init
Fix lint
Invert conditional order to make fn more readable
Don't keep a copy of elems, always recalculate

Elems is a pairing of dom elements to search clauses. For (upcoming) stewardship searches, the key and predicate change dynamically to contain model information based on the model the user selects in the dropdown. It will be required to recalculate this on every search.
Add support for udf collection searches

Make applySearchToDom called through searchBar so that it can in turn call the downstream method on a udfcSearch instance. This is required so that search.js doesn't have to init() udfcSearch, or import it at all.

Make a helper template tag.