Comment 2 for bug 534284

Fix released!

Features:
Updates thumbnails for both images and image sequences at the timeline depending on their start frame.
Is quite fast. I can't spot that much of a difference, but my computer is pretty new, though.
Uses the file thumbnail image (shown in the treeview) if the clip starts at 0.00.
Gives the thumbnail images the names file_extension_2 and up, and put them in the thumbnail folder.
Removes unused thumbnails, to not clutter the folder.
Rebuilds the thumbnails folder if lost, which possibly could be a fix for #512516. This was implemented due to the next point.
Should be backwards compatible, i.e. old projects should also load.
Otherwise, works as expected.

The patch is 1.4.0-alpha based.