Webapi-Swagger : Generate `ToX` and `FromX` instances based on ContentTypes

[kahlil29]

Currently we are blindly generating ToJSON and FromJSON instances for generated types in Types.hs.

We need to have a look at ContentTypes (if set) in the Contract in order to decide and generate the appropriate (ToJSON, ToXML ...) instance .

We probably need to pass the ContentType data in the State and read it when generating the types.