#4 Need to support description/note per item in sets

[Patrick Schmitz]

The sets functionality allows users to create narrative with and about a set of items from the larger collections. In order to support this, they will often want to describe why a given item is interesting to them, or why they put it in the set. This requires a note for each item, and not just for the set as a whole. It also provides a caption for obvious visualizations like slide shows.
All this needs is another column in the obj_sets table, and UI to add and view this.