0.8.6: Remove Unassigned Materials + List Unlinked Image Nodes

Remove Unassigned Materials:
- Remove empty material slots and materials that are not assigned to any vertex.
Find it on the Material Specials menu (black arrow, right of material slots list)

List Unlinked Image Nodes:
- The "List Missing Links" operator now also lists Image Nodes that have its outputs not linked to anything.