add auto management of admin SSH keys

right now there's no systematic way for admins to disseminate new SSH pubkey info to the testing servers. this should be managed the same way any other overall change is managed -- by committing the info to the central package, and running the script on all the servers.

should be pretty easy to adjust the script to always create a new authorized_keys file for all existing admins on the system -- if an admin desired multiple SSH keys, that could easily be put in the ssh key variable as well.