Add option to generate schemas for request and response bodies

Currently JSON-Schemas are only generated for definitions in the `definitions` or `components/schemas` section. This is alright if your full request and response bodies are defined there, but that is not always the case in every OpenAPI spec. It would be nice if `paths///requestBody/content//schema>` and `paths///responses//content//schema>` could also be traversed.

The generated filenames will probably be long and ugly, but that is something I can live with.