Images with Links are not shown if anchor is activated

[kreuzberger]

If an image is embedded in a link, e.g. <a class="reference internal image-reference" href="images/gradient_600x600.jpg"><img src="images/gradient_600x600.jpg" alt="unscaled gradient"/></a>, the activation of the link shows then the "binary" content instead of the image itself.
Like with other browser implementations, the link should lead to

• show the image in an extra window (browser window or some window above)
• Window must be closable or if shown in browser must be part of the forward/backward stack

[kreuzberger]

As request from @rear1019 the behaviour should be different:

1. The image should not open in an modal windows above the browser window, it should be display in the browser widget itself.
2. Invalid Urls should not be considered.
3. If an image url is clicked, it should be fitted to the current widget size. If clicked a second time, the size should be changed to original size with scrollbars. A third click should show the image fitted again.