Option to make machine suggestions for confirmed images

[StephenChan]

Motivation: I'm pretty sure there have been a few Q&A threads by now (recent example) which shows that some folks want to test their source's classifier on images that are already confirmed (e.g. as a sanity check) - and when they do, they end up having to either delete annotations or upload copies of the same images.

We could add a source-level option which would allow image classification to be queued not just for unannotated images, but also for confirmed images. The option would be off by default because most folks probably won't need this and it consumes AWS Batch resources.

When using this option, folks will generally want to export the machine suggestions to CSV, alongside any confirmed annotations that those points happen to have. CSV annotation exports should already allow this, but it's definitely worth a double check.

Note: Quite a few images on CoralNet already have both confirmed annotations and machine suggestions. These are the images which had machine suggestions added first, then had annotations confirmed, and didn't have a new classifier trained since then. We simply don't allow things to happen in the reverse order yet: have annotations confirmed, then have machine suggestions added. Also note that in this case, the suggestions would only exist as Score instances, not as Annotation instances.