Add ability to get average rating for a user over all categories
Add ability to get average rating for a user over all categories

predatell/agon-ratings,arthur-wsw/pinax-ratings,GeoNode/geonode-ratings,rizumu/pinax-ratings,pinax/pinax-ratings,rizumu/pinax-ratings,GeoNode/geonode-ratings,arthur-wsw/pinax-ratings,predatell/agon-ratings,arthur-wsw/pinax-ratings,GeoNode/geonode-ratings,pinax/pinax-ratings,predatell/agon-ratings,pinax/pinax-ratings,rizumu/pinax-ratings