Fix style creation/update for multi-instance module.

We now properly take into account the multi_priority value in
the SQL statements. We want to get the last active distincts items
for the tuple (opearation,multi_priority).
Add multi_name as opration suffix when listing style items.

This is displayed in the style dialog. With this fix we can now
distinguished between multi-instances.
Merge branch 'fix-style-multiinstance'

* fix-style-multiinstance:
  Add multi_name as opration suffix when listing style items.
  Fix style creation/update for multi-instance module.