Always pass enclosing class or enum to annotator methods (changes method signatures)

[joelittlejohn]

This allows annotators to refer to classes that aren't on the classpath, which in turn allows jsonschema2pojo to support integration with new libraries without introducing a runtime dependency on those libraries.

To do this, every method on the annotator needs to be given a way to grab the current package, or some other construct that can refer to classes directly using a fully qualified name.

This is a breaking change since many of the annotator method signatures need to change to include the class or enum currently being worked on.