Adding link_attrs to column.

Add the ability to attach attributes to a column containing a link via
the link_attrs property.

The new link_attributes parameter will eventually replace the less
general link_class attribute.

Co-Authored-By: Davide Guerri <davide.guerri@hp.com>
Change-Id: Iea79aec970a2fe8711a9f5a8b973407df88dcdec
Implements: blueprint add-attribute-links
Closes-Bug: #1298533
cannot add users to groups

Correcting a javascript issue where the modal popup dialog
for adding users to groups was being disposed / detached right away.

The code removed does not seem to be needed or used anywhere.

Change-Id: I299afef6da1c9bc7ab8668f44d08a67219777761
Closes-Bug: 1336560
Merge "Adding link_attrs to column."
Merge "cannot add users to groups"