Move child loading into DivinerAtomQuery and collect/organize more data on class Atoms

Summary:
Ref T988. This is extremely rough looking in the UI, but gets most of the information we need into the right places.

The controller rendering code is super rough too, I'm going to break that up shortly.

• Add needChildren() to DivinerAtomQuery.
• Compose and organize class methods when rendering classes. The old Diviner was not smart enough to do this, so a class would only document methods which the class itself implemented, not methods inherited from parents. I'd like to show those too to provide a more complete understanding of how to use a class (but they'll be marked with "inherited" or somesuch). This code walks the "extends" list and builds all of the class methods, annotating them with where they are defined and where they are implemented.
• Coompose and organize "tasks". The old Diviner was not smart enough to do this, but I want to reduce the amount of duplicate/busy work involved in documenting subclasses. In particular, I want them to inherit "@task" declarations from parents so that class trees are more cohesive. They now do so.

Test Plan: See screenshots.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T988

Differential Revision: https://secure.phabricator.com/D6823