Initial support for record types

[mattrpav]

1. Generate record type objects
2. Unmarshal into constructor-only instantiation (or is direct field access available?)
3. Consider generating record types in a separate package or as a second type next to the POJO with a 'Record' suffix for the name.

ie. Order, OrderRecord, Item, ItemRecord, etc

Marshalling should be unchanged (use getters or fields)

[laurentschoelens]

Linked issues in JAXB-RI 1659 and JAXB-API 183