Whenever the server returns true for the can-assign Webdav property of
a system tag, it means the current user is allowed to assign,
regardless of the value of user-assignable.
This commit brings the proper logic to the web UI to make it possible
for users to assign when they have the permission.
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
Joas Schilling
Vincent Petry
Joas Schilling