(PE-4372) Added utilities for alt dns names

* Able to add extensions to a CSR
* Added utilities to create an Alt. DNS names extensions

This PR is for review only so people can start taking a look at it while I write some tests.
jeez, that sucks.  It feels really shaky to me to not have a way to test that even a little bit... but I'm not sure I'm willing to flush 2 days on it... at the very least we should have a jira for it.

what do other people think?