Generate some amount of PHP class documentation

Summary:
Ref T988. This brings the class/interface atomizer over. A lot of parts of this are still varying degrees of very-rough, but most of the data ends up in approximatley the right place.

ALSO: PROGRESS BARS

Test Plan: See screenshots.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T988

Differential Revision: https://secure.phabricator.com/D6817