Add Backlinks to Special:(Change|Remove)Credentials

Add Backlinks to Special:(Change|Remove)Credentials

If an user wants to change or remove more then one set of credentials, he has
to know that he has to remove the parameters from the special pages in the url
bar of the browser or has to click through the workflow, which he used to view
the special page for the first change/remove.

This change adds a backlink to Special:(Change|Remove)Credentials when there was
a success of the change or remove of a credential. This link helps the user to find
back to the special page to change or remove a second set of credentials, if he wants.

Change-Id: Icd459518b258b7e717ca113829add6597eb6e7b8