relations: list views for reverse relations

[gythaogg]

It would be nice to be able to select a relation from the nav bar menu also using the reverse name (as we are able to while creating relations in the detail page). We could choose to show them in pairs, if we do not want the list to get too long. The ability to search both forward and reverse names in the menu would be handy.

The list view should show the relations in reverse.

Note: If we do show the relations in reverse then we also need to allow the creations of these relations in reverse (using the Create button in the List view)