Load/saving fix and framebuckets

Fixes a bug where loading a config setting would unload everything after it due to it triggering the auto-saving logic mid load. Which caused it to save the default values for the other settings.

Added support for video frame buckets, specify a list of valid buckets for export, this ensures the exported images/videos are in the right length, frame buckets of length 1 are treated as images (and converted to png).