* Fix using wrong public key in sign-self-issued
* Change behavior of TTL in sign-intermediate
This allows signing CA certs with an expiration past the signer's
NotAfter.
It also change sign-self-issued to replace the Issuer, since it's
potentially RFC legal but stacks won't validate it.
Ref: https://groups.google.com/d/msg/vault-tool/giP69-n2o20/FfhRpW1vAQAJ
* Add pki/root/sign-self-issued.
This is useful for root CA rolling, and is also suitably dangerous.
Along the way I noticed we weren't setting the authority key IDs
anywhere, so I addressed that.
* Add tests