msva-perl should handle alternate certificate formats
as of 0.5, the only cert formats msva-perl can interpret are x509der.
we should probably also handle:
- x509pem
- opensshpubkey
- "rfc4716":http://tools.ietf.org/html/rfc4716
- "openpgp":http://tools.ietf.org/html/rfc4880#section-5.5.1.1
- "openpgparmored":http://tools.ietf.org/html/rfc4880#section-6.2
(from redmine: created on 2010-10-27, closed on 2010-12-26)