A few fixes and improvements

[vletroye]

Hi There. Let me first apologize if not complying with a 'state of the art' use of GitHub. I am far from confortable with the Git commands...

Here are a few fixes:

• Fix use fo 'ESC' which could be pressed in various situation and toggling fullscreen/normal screen, missing the layout when stopping/re-starting slideshow.
• Fix cycling in slideshow mode when reaching the first/last images

And a few improvements (at least as far as I am concerned! It's a matter of point of view)

• Instead of loading "big" images in the current page, I open them in fullscreen mode, just as made by the slideshow
• I did also attempt to add a smooth transition between images in slideshow mode (a dirty solution).
• Finally, I wanted to lazy load the images while scrolling in the pane/linear-pane. This is really not yet perfect, especially with IE/Edge* but works fine enough for me, within Chrome. (*: I notice mainly perf issues/freeze)