The addressbook used to crash when someone issued the alias and

The addressbook used to crash when someone issued the alias and
unalias commands while on that menu.  This patch has a basic fix for
this behaviour, and adds delete and undelete functions to this menu.
While I'm on it, I've also made sure that "apply-tag" untags
everything on all menus.

The original crash was noted by Oliver Kauss <kauss@gmx.de>.