Add tasks count to sites
Change site id to mini site id for tasks
Annotate task models
Add tasks relationship to sites
Return the first mini sites photos. Fix #348
Merge pull request #358 from calblueprint/mark/api/sites-counts

Sites have mini_sites_count and tasks_count
Merge pull request #359 from calblueprint/mark/api/site-photos

Return the first mini sites photos. Fix #348
Add planted_at to mini_sites
Add planted_at to the mini_site base serializer