(DRF 3.0) Added missing default style for FileField

[kchang]

The browsable api forms were missing file inputs for FileField. This was easily added by including the information in HTMLFormRenderer.default_style

Before:

After:

[lovelydinosaur]

Good catch yup!
The styling seems a little odd - wasn't really expecting the white surround. May be worth looking at (we can always have a separate template for file inputs if needed?

[kchang]

Taking out class="form-control" removes the white outline box around the file input.

After:

[lovelydinosaur]

I've avoided block overriding at all costs so far.

Either we can:

• Have form-control be something that's passed to all other input fields except file in the context.
• Not write form_control if style.input_type == file.
• Go with what you have here, but be explicit rather than using block overriding.

Additionally we need to make the same fix for the vertical and inline styles.