Fullscreen Mode Suggestions

[jmnduc]

In Fullscreen Mode, I would like to suggest:
- Allow to move the small thumbnail (even though the thumbnail can be sized, it's still stuck at the the bottom right and that part might need to be seen)
- Allow to change the opacity of the small thumbnail
- Have the current rectangle selection view inside the small thumbnail (I hope you understand what I mean) a little bit different (like whiter, darker or another color) so that it's easier to locate the rectangle selection view in the thumbnail because a rectangle with small border is harder to see
- Allow user to choose the mouse buttons as next/previous file like before

[jmnduc]

And also when there's a click on the thumbnail outside of the rectangle area, the rectangle area centers to the clicked area