Blender Git Loki

Followup for fix T37718: image was not saving with proper settings second time

This was actually a regression after color management re-implementation, need
to copy settings from saved image buffer to an original one since they might
be modified during save.

Also noticed image format planes detection didn't work properly from an image
buffer. Made it so save operator works fine now, but also marked a TODO in
BKE_imbuf_to_image_format() which needs to be investigated further.