Add links to images in self contained report

[davehunt]

When --self-contained-html is used we should provide links to any images in the HTML report. We should avoid duplicating the large data URI values, so it makes sense to use JavaScript to enable this functionality.

The links in the report column could be hidden by default and displayed via JavaScript, and the href destination could be taken from the associated img src. Similarly, the img could be an inactive link, enabled via JavaScript if enabled.

[PhilippSelenium]

I should have read the comment before I commited my pull request :(
In this case I can't fix it. i don't know any javascript.