Develop 2.0 - support binary input and output

[boazsapir]

This replaces #1166 with a new implementation based on the conclusions of the discussion in OAI/OpenAPI-Specification#50

These changes in swagger-model are a precondition to the changes that are needed in swagger-codegen in order to support binary input and output. Once this request is merged, it will be followed by another pull request to swagger-codegen.

[BigSocial]

I guess this solves my issue #1531 assuming core will map the InputStream parameter (see my example) to "type" : "string", "format" : "byte" and codegen and UI understand the same thing.

I'd make a few points:

1. "type" : "string", "format" : "byte" is a confusing way to encode this. "type" : "binary" seems much more clear but I guess there are reasons...
2. @webron asked in Clarify 'byte' format OAI/OpenAPI-Specification#50 "Do you think that, in the case of "format" : "binary", the content type "octet-stream" should be mandatory?" I believe the answer is very much "no" since there are any number of MIME types that one might want to deal with this way e.g. all the image types, application/pdf, application/msword, etc.
3. Every popular object storage REST API including S3, OpenStack, Box, DropBox, etc. require PUT or POST of binary data with no encoding to upload objects. I point this out to make it clear that this is not a fringe use case for anyone dealing with binary files such as images, documents, presentations, etc.