Allow "file" as parameter type

[Konafets]

Consider the following description of an operation:

...
'doMultiPartLocation' => [
    'httpMethod' => 'POST',
    'uri' => '/multipartLocation',
    'parameters' => [
        'foo' => [
            'type' => 'string',
            'required' => false,
            'description' => 'Testing multipart request location',
            'location' => 'multipart'
        ],
        'file' => [
            'type' => 'any',
            'required' => false,
            'description' => 'Testing multipart request location',
            'location' => 'multipart'
        ]
    ],
    'responseModel' => 'MultipartResponse'
],
...

$client->doMultiPartLocation([
    'file' => fopen('test.html', 'r'),
]);

There is only 'any' as a valid file type available to specify the parameter. We should add 'file' here.

[GrahamCampbell]

Closing since stale - I'm doing a cleanup across the whole organization, to enable us to focus on the tickets that are still live and have interest. Please feel free to open a new issue if this still is important to you. :)