New hammer utility feature in HEAD: 'hammer cleanup'

[Thomas Nikolajsen]

. .
>    'hammer cleanup' will do the following:
>
>    * Locate all mounted HAMMER filesystems, including PFS's mounted with
>      nullfs.
>
>    * Create <fs>/snapshots and <fs>/snapshots/config if they do not exist.
. .
`config' is somewhat anonymous;
could it be change to cleanup.conf or maybe hammer-cleanup.conf,
or if non cleanup stuff is going to it in the future just hammer.conf?

A man page for it could then be made, for users to ponder in.

Also it might go to a subdirectory, eg. snapshots/etc,
with the other book keping files (period and cycle);
I guess users prefer snapshots in this directory

 -thomas