JENKINS-8615: To me, "EC2 RSA Private Key" means the private part of the X.509 certificate you use to sign requests to AWS APIs, but what the hudson-ec2 plugin wants is a EC2 key pair. I think this could easily be clarified.
2) Hudson -> Jenkins in the desciptions.
3) Clarify help on the user name
4) Move the Root command prefix out of the advanced properties since it's used most of the time now.
5) Various other wording changes