zsh completion: update mq commands completion * add qclone command; * qapplied/qunapplied: add --last/--first; * qdiff: add all diff options; * qfold: add --force, --no-backup; * qgoto: add --keep-changes; * qimport: add --git, --push; * qnew: add user- and date-related options; * qpop/qpush: add --keep-changes and --no-backup, drop --name; * qpush: drop deprecated --merge; * qrename: complete only unapplied patches' names; * strip: add --rev, --keep, --bookmark, update descriptions, drop --backup.