Modified resource retrieval from gs_catalog in layers/models.py and added assumption that store exists within workspace in updatelayers to improve speed.
Merge remote-tracking branch 'upstream/master' into layer_geoserver_speedup
Updated code to obtain gs_resource in models(layers) to use gsconfig get_resource function with workspace and store passed.  Fixed issue with gs_slurp and error handling for nonexistent workspaces
Remove some unnecessary debug lines
Fixed issue with var reference names in get_resource() call in Layer.store_type property function
Merge branch 'master' into layer_geoserver_speedup
Merge branch 'master' of https://github.com/GeoNode/geonode
 Merge branch 'master' of https://github.com/GeoNode/geonode
Merge branch 'master' of https://github.com/GeoNode/geonode
Merge branch 'master' of https://github.com/GeoNode/geonode
Merge branch 'master' of https://github.com/GeoNode/geonode
Fix the importer upload. Fixes #1312.
Initial add Groups redux
geonode group security redux
Clean up the groups tests.

* Explicitly import the Group and GroupInvitation classes.
* Add a test case to make sure the token URL route works when a user is invited to a group.
Use is instance vs type when determining class type of an object.
Check group permissions in layer_acls
Check groups in search perms
Fix import in security/auth.py
Commenting out GroupLayer and GroupMap Foreign keys due to circular imports