R1:d0af617818b6

Add "final" to (almost) everything else

Summary: Last of the big final patches. Left a few debatable classes (12 out of about 400) that I'll deal with individually eventually.

Test Plan: Ran testEverythingImplemented.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, epriestley

Maniphest Tasks: T795

Differential Revision: https://secure.phabricator.com/D1881