add a free-form comment field per-annotation

[joefutrelle]

The user will be able to optionally write a comment when creating or verifying an annotation, and view comments along with the annotations for a ROI. For verification, if the user doesn't enter a new comment, the previous comment (if any) should be retained.

[mike-kaimika]

@joefutrelle Are the comments going to be a one to one relationship with the annotation? Or could there be more than one comment on each annotation (one for the original annotation, one for the verification, maybe more?)

Going to assign this to @MattCharron32 to take a look at the UI

[joefutrelle]

one-to-one.