Targeted metadata display panel

[waxlamp]

We would like one of the panels to show certain metadata values, and optionally include means to edit some of them.

For instance, imagine that the task in a given experiment is to grade a tumor in the image. The tumor grade could be included as metadata, and the panel display could show a dropdown menu allowing the subject to select from a finite menu of choices (i.e., typing that metadatum as an enum of strings, and providing the appropriate UI for that type).

This issue may require implementation of a spec for what to show, and how, perhaps itself stored as metadata.