Disabled MoveToAction for Tags/TagSets

Just disables the 'Move to Group' menu item when Tags/TagSets are selected; until it's sorted out what exactly should happen, when Tags are moved to another group.
See https://trac.openmicroscopy.org.uk/ome/ticket/12226

Test: You should still see the 'Move to Group' context menu item when selecting Projects, Datasets, etc. but not on selection of Tags or TagSets.