Check a user's group permissions in objects_with_perm.
Add a post_save hook to create default permissions on new resource base objects.
add set_default_permissions and set_permissions to PermissionLevelImixin
use group.slug in ajax_lookup
Move to using set_default_permissions and set_permissions from PermissionLevelMixin in Layers, Maps, Documents
Merge branch 'groups-redux' of https://github.com/garnertb/geonode into groups-redux