Reorganize roxygen documentation for reporters

[jayqi]

The roxygen documentation for reporters is not especially usable. Documentation on methods is spread out across the articles for the Abstract classes where they are implemented, and the articles for the user-facing reporters are barebones.

I propose we create comprehensive roxygen docs for each of the user-facing reporters by stitching together sections with @inheritSection. See the roxygen for DirectedGraph for what I'm thinking.