bookmarks: add explicit option to list bookmarks of the given names
This is a generalized form of the --active option.
A redundant sorted() call is removed. There was no point to update dict items
in lexicographical order.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state