Add easy-to-use RFC 6962 types
The structures that make sense for TLS (de)serialization and JSON (un)marshalling aren't necessarily the best way to interface with the actual content. For example, we should be as helpful as possible and provide typed content like x509.Certificate rather than pretty raw byte slices.
Adding this issue as a placeholder to try and define an easy-to-use API that interfaces seamlessly with the more detailed types. Not sure if it makes more sense to focus on this as a separate step or not, let's see. Worth keeping in mind, but I suspect the answer is "both".