Removed some icons I previously added in the wrong place.
importlayers now display a message to the user when stopping the process because --overwrite was not set and a layer with this name already exists
Merge pull request #760 from capooti/importlayers

importlayers raises a message when skipping importing an existing layer and the --overwrite option was not specified
Added some django-admin goodness to search, filter, date sort most of the models in admin.
Added verbose_plural_name in meta for TopicCategory model.
Update the geonode auth url entry in jenkins-geonode-aws.sh
Merge branch 'master' of github.com:GeoNode/geonode