Meta-annotation to restrict on what types a qualifier may appear

Here are two distinct concepts:

• where an annotation may be written in source code.
• what types may be qualified by a given qualifier. This is a restriction on the effective qualifier on a type, after application of implicit type qualifiers, defaults, and flow-sensitive refinement.
  The concepts are different. The Checker Framework forbids users from writing redundant qualifiers in some situations, for reasons of brevity and consistency.

The first concept is indicated by @TargetLocation. The Checker Framework has no convenient declarative mechanism for specifying the second concept. It would be nice for the Checker Framework to have such a construct and to automatically enforce it.

Start by reading the existing @TargetLocation mechanism and the Checker Framework's handling of effective qualifiers after implicit qualifiers, defaults, and flow-sensitive refinement. The issue is complete when a declarative restriction for qualifier-applicable types exists and is enforced automatically, but no files or tests are identified here.