Image streams were initially separated from video streams, but they're now
joined with a parameter defining if they're a still image, image sequence,
or regular video. The image sequence import process has also improved so
that if images from the same sequence are imported too, they'll either be
ignored or the user won't be asked again for those if they should be an
image sequence (fixes#1193). Also shifts decoder "probe" process to return
an item, useful if the decoder returns a non-footage item.
itsmattkc
6db591e89f