Revamp user_capabilities with new copy fields

Add copy fields corresponding to new server-side copying

Refactor the way user_capabilities are delivered
 - move the prefetch definition from views to serializer
 - store temporary mapping in serializer context
 - use serializer backlinks to denote polymorphic prefetch model exclusions

awx/api/generics.py

@@ -355,13 +355,6 @@ class ListAPIView(generics.ListAPIView, GenericAPIView):
     def get_queryset(self):
         return self.request.user.get_queryset(self.model)
 
-    def paginate_queryset(self, queryset):
-        page = super(ListAPIView, self).paginate_queryset(queryset)
-        # Queries RBAC info & stores into list objects
-        if hasattr(self, 'capabilities_prefetch') and page is not None:
-            cache_list_capabilities(page, self.capabilities_prefetch, self.model, self.request.user)
-        return page
-
     def get_description_context(self):
         if 'username' in get_all_field_names(self.model):
             order_field = 'username'