These methods are just a copy of the ones in [SshKeys](https://github.com/jclouds/jclouds/blob/master/compute/src/main/java/org/jclouds/ssh/SshKeys.java), which are private. I added them here to be able to build and test the provider, but all the methods in this DSAKeys class should be moved to the SshKeys one.

I plan to open a pull request and move them there, but I'd like to do it after having this PR in. Do you agree?