[Spring] fix datatype for non-multipart file request body

[quackes]

fixes #2191

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Description of the PR

The distinction between the following cases was leading to compile errors in the generated code

adressing request body as single file:

requestBody:
  content:
    application/octet-stream:
      schema:
        type: string
        format: binary

and files in multipart/form-data requests:

requestBody:
  content: 
    multipart/form-data:
      schema:
        type: object
        properties:
          id:  
            type: string
            format: uuid
          profileImage:  
            type: string
            format: binary

(as described here

I found out, that internally multipart parameters are handled in formParams, where the "raw" body is handled in bodyParams.
In the template for formParams is a special case for files in multipart, that was also used for rendering the delegate methods signature.
But request bodies as single file were ignored in that case.

I added the distinction in the template part for the delegate methods signature.

I invoked the sample generation scripts, they did not change any files.

@bbdouglas (2017/07) @JFCote (2017/08) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01)

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[wing328]

Tested locally and didn't notice any issue.

[anuhyapolisetti]

We still see this issue for the generated Api and ApiDelegate files, they have different request body types (Resource/MultipartFile), which is resulting in compilation errors. opened a new issue at #3905