Add standard delegating (or adapting) deserializer, serializer

[cowtowncoder]

It is sometimes easier to implement serialization and/or deserialization by using an intermediate type that Jackson knows how to handle (read/write from/to JSON), and then convert between that intermediate type and target Java type. This is called "adapter" in JAXB, and "delegatee" for Jackson creators.

It would make sense to implement abstract generic-type base classes (like StdDelegatingSerializer, StdDelegatingDeserializer), which takes care of the delegate-handling part, and only requires implementation of converter methods to go between intermediate and target types.

[cowtowncoder]

Implemented.