Commit a large bevy of bugfixes for lumina-fm
1) Make the image thumbnail viewing dynamic, so now it will only load the images that are actually visible in the viewport (greatly reducing memory consumption for massive collections).
2) Fix the copy/cut paths with the ne backend.
3) Make sure that the slideshow viewer does not load thumbnails in the list (same memory issues).
4) Make sure the context menu is available even if an item was not under the mouse.
5) Fix the context menu availablility for items depending on permissions, etc.
Merge branch 'master' of github.com:pcbsd/pcbsd