Add some stuff

I added some stuff I using in my project that can be useful for other devs. What you think?

- CamelCaseModelType option to SwaggerSpecConfig for generate model type in camelcase.

- Response xml docs:
  <response code="HttpCode">Message</response>
 I know this dont exists but its make much easier to add custom response messages for methods.

- Option for use separeted xml docs for model.