"quick" option to DDRLocalCollection.entities()

With the quick option, Collection.entities() will return a
quick-and-dirty fake Entity object with only the fields we need
for a list, rather than loading a real one.
mv collection entities list to a separate view

Collection-entities is now a separate page rather than a tab on
collection-detail.  The back button from entity-detail to entities
list page should now work the way you'd expect it to.
Collection-detail should now load fast since it doesn't have to
also load and display all the entity info.
List is paginated, though Bootstrap pagination doesn't quite work.
mv entity files list to a separate view

Entity-files is now a separate page rather than a tab on entity-detail.
The back button from file-detail to files list page should now work
the way you'd expect it to.  Entity-detail should now load faster
since it doesn't have to also load and display all the files.
List is paginated, though Bootstrap pagination doesn't quite work.
Merge branch '164-list-pages'

Conflicts:
	ddrlocal/ddrlocal/models/__init__.py
	ddrlocal/webui/templates/webui/collections/detail.html
	ddrlocal/webui/templates/webui/entities/detail.html
	ddrlocal/webui/urls.py