Add image format and source information to display (#1567)

Add image format and source information to display - needs changes to engines to actually display something. 

Displays result.source (website from which the image was taken) and result.img_format (image type and size).

Result is styled with result-format and result-source classes. See PR #1566 for an example of an engine which has the necessary changes.

Strip <span class="highlight">...</span> in the oscar image template.