consider adding field to schema for countermeasure categories (tags)

[kristovatlas]

Such categories could include Quality, Usability, and Feedback, or any other categories. All categories would be listed in a new array.

[kristovatlas]

Actually, I think it makes more sense to just generalize this as "tags" that can be applied to various levels, for now.

[kristovatlas]

the tag object should include a bool attribute "include-in-docs" to determine whether the tags will be printed within threat model tables in generated documentation files