Replace made-up use of "topographical" ordering with professional, high-quality academic use of "topological" ordering

Summary:
Ref T13325. See PHI1271. The word "topographical" is misused in a couple of APIs here when we mean "topological".

We also have a function which produces a "topological" ordering of a graph which may contain cycles, which isn't a real thing and can't really have a good name, but this is now "rough topological ordering".

Test Plan: Ran unit tests, grepped for topograph.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13325

Differential Revision: https://secure.phabricator.com/D20597