[Hans] allow entry of null scan decisions ( annotations) on a scan

[curtislisle]

Currently, a user has make a scan decision (usable, unusable, etc.) in order to store a note on an image. Then MIQA advances to the next scan.

If we provide a "save a note" or save annotation button in addition to the scan decision, the user can make multiple "annotations" on a single scan. This is close to Hans' desire of making multiple annotations on a scan in a single session. This "annotation" has a null field for the final decision.