Move to the categories count method suggested by ischneider. Thanks @ischneider
move counts to base tag
fix tests
Merge branch 'master' of https://github.com/GeoNode/geonode into new_counts

Conflicts:
	geonode/base/models.py
	geonode/layers/tests.py
Merge pull request #939 from simod/new_counts

New counts for topic categories