Orphaned missing (rebased onto develop)



This is the same as gh-2549 but rebased onto develop.

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To test this PR
 * Go to the Project tabs
 * Click toggle between order alphabetically and by date.
 * The orphaned folder should still be visible and should be the last one. 
 * Check that objects are correctly ordered.

see https://trac.openmicroscopy.org.uk/ome/ticket/12294