Remove PreserveGetQuerySet mixin. Update SingleObjectList and

MultipleObjectFormActionView views to use a new get_object_list method.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/statistics/views.py

@@ -19,7 +19,7 @@ class NamespaceListView(SingleObjectListView):
     template_name = 'appearance/generic_list.html'
     view_permission = permission_statistics_view
 
-    def get_queryset(self):
+    def get_object_list(self):
         return StatisticNamespace.get_all()
 
 
@@ -36,7 +36,7 @@ class NamespaceDetailView(SingleObjectListView):
     def get_namespace(self):
         return StatisticNamespace.get(self.kwargs['slug'])
 
-    def get_queryset(self):
+    def get_object_list(self):
         return self.get_namespace().statistics