Refactored validate-input directive.

- now used as attribute instead of element
- dependent on ng-model
- updated usage
Added input directive for input[type="file"]
conditionally showing a file field based on the named parameter type
Don't trim non-strings in try-it parameters.
Allowing for file uploads in try it

- conditionally using FormData in requests 
- defaulting media type on the try it form
Merge branch 'features/ajax-file-upload-58524000'