Upgrade serialization code

[ekolis]

Describe what needs to be improved.

The serialization code in Nova is seriously out of date; a lot of classes seem to handle the task of their own serialization into XML. We could upgrade this to use another more automated method of serialization, such as System.Text.Json or the FrEee serializer.

Describe how this change could impact the quality of the code.

This could eliminate a lot of boilerplate code, which could be replaced with attributes directing the serializer to treat certain properties in certain ways.