Reorganize Serialization Code

[jsallay]

The serialization code is kind of messy and not extensible. We already have an additional case for base64 encoding. It would be really nice to additionally convert to/from other formats such as json and yaml.

I think we should try to define an interface where a user needs to define a class with a few functions for serialization and deserialization. When serializing, the class to use would be a template parameter. This would make it easy to switch between different formats.