Replace made-up use of "topographical" ordering with professional, high-quality academic use of "topological" ordering
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.
Reviewed By: amckinley
Maniphest Tasks: T13325
Differential Revision: https://secure.phabricator.com/D20597