Blender Git Loki

Fix T37481: Image Sequence can't be loaded

Allow loading of image sequences in addition to single images in the open image operator

I solved it by adding the possibility to load an image sequence in the Load Image Operator.
The image user is passed in the operator customdata now as well, best solution for now, but general handling of image user still a bit weak. The offset and length of the image sequence is now calculated in the image open operator by storing all found frames in a list and sorting this list.

Reviewed By: campbellbarton, brecht, lukastoenne

Differential Revision: https://developer.blender.org/D209