Add sshroot --- krbroot for ssh-agent

Add sshroot --- krbroot for ssh-agent

The goal here is to make it easy to have one set
of ssh keys that you use frequently and want to
be able to not expire and stuff, and have one
set that you use for root or otherwise sensitive
access.

This version has a bunch of issue --- prominently,
it doesn't try to unlock keys particularly --- but
does mostly work.