Generate model (POJO) from swagger.json for light-rest-4j generator

[stevehu]

We have used swagger-codegen before and it can generate the model. Let's bring this feature to light-codegen as some people ask for it.

[stevehu]

I did evaluate jsonschema2pojo and it is not designed for this. It works with only json schema not swagger like schamas. Also, it doesn't support $ref as it deals with individual schema and $ref must be external.

[stevehu]

Given it is very hard to get the proper name for inline schema and duplicated sub schema, it is decided that we will only generate model from definitions section after discussed with @ddobrin. This will require whoever create swagger specification to extract reusable models into definitions.