Trashcan display item owned by other users in some cases

[Nicklas Nordborg]

If logged in as a user with admin permissions this user is able to see other user's removed Bioassaysets and Transformations. Maybe other items as well. I think the problem appears because the 'ownedBy' filter that is activated doesn't apply to Bioassaysets and Transformations since they don't have an owner of their own. They belong to the owner of the experiment. It could also happen for other items which implement the 'Removable' interface but not the 'Ownable' interface. I don't know if there are other such items, we need to check that.

Note however that the permissions are checked and only items which the logged in user has DELETE permission for are shown in the trashcan in all cases. Thus, this bug only affects user's logged with admin privileges.

Also note that this bug also makes News, File types, and other items which neither have a direct or indirect owner to appear in the Trashcan. In this case it is a good thing that they do since otherwise there is no way to delete such items permanently.

[Martin Svensson]

(In [3142]) Fixes #493 Trashcan display item owned by other users in some cases