Make /groupadd «group» syntax to add the selected JID in the roster to the group.

I would appreciate to be able to add the selected contact into a group instead of typing his/her JID.

So instead of
/groupadd «jid» «group»

Do

Select contact → /groupadd «group»

• Changesets:
  • Revision b7c23313 by mathieui on 2016-08-25T18:22:01Z:

Fix #3217 (allow /groupadd "group" with selected row in the roster)