Permission text now doesn't appear when all permissions are there, or
shows as "invisible" or "not assignable", which should better cover all
use cases.
Changed select2 style to use boxes in the input field.
For admins: display the namespace behind the tag name.
For users: no namespace, don't display non-assignable tags in the
dropdown, display already assigned non-assignable tags with a different
style
Jan-Christoph Borchardt
Vincent Petry
Erik Pellikka