Add controls for printing and saving about bigpicture

[henrygd]

The issue with downloading is that the download attribute only works if the image / video is served from the same domain, which is often not going to be the case. And you can already download by using the context menu, video controls, or long pressing.

For printing, the only way to do this that I'm aware of is hacky and verbose, and I'm not sure that it'll work across different browsers and devices. And like downloading, I'm not sure it's a common enough want to justify the additional weight of the icons and functionality. Users can always save the image or open it in a new tab, then print from there. My opinion is that both cases are covered well enough by default browser functionality.

But I will leave this issue open for a while and if others think it would be a good addition I will look into it further.