21179 - Publish the ssh key security plugin

Complete rewrite of the sshkey security plugin.
21434 - Sshkey security plugin should allow the use of authorized_keys client side

This commit adds the ability to use an authorized_keys file for
verification on the client in cases where host verification checks are
not desired.
Correct the config field name in README
Deal with known_hosts files with multiple aliases per key.

You can comma seperate a list of hostnames this machine may be known by in an ssh_known_hosts file.

Ergo we need to split on , and process each hostname individually
Add a test for hostname not the first field in known_hosts
Bump version and update changelog
22172 - Mcollective ssh key security should allow a custom per-identity authorized keys file

mcollective is a long running process which is run as a daemon. It's never correct for the _server_
to use the user who starts it's agent forwarding to verify things with, as this will stop working
as soon as the user who started the daemon logs out
22172 - Mcollective ssh key security should allow a custom per-identity authorized keys file

Be able to interpolate the username into authorized_keys path

We don't want users to be able to add arbitrary ssh keys without oversight,
ergo we push out a set of authorized keys files to machines with puppet
in a directory the user doesn't have write access to.
22172 - Mcollective ssh key security should allow a custom per-identity authorized keys file

Bump version and update Changelog