Apply various linter fixes.

Summary: Applied various linter fixes. Also make the `.editorconfig` file a bit more specific. Unfortunately, `arc lint --apply-patches` currently modifies some test data that it shouldn't, but this should be fixed after T5105.

Test Plan: Ran `arc unit` to make sure things weren't broken.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin, aurelijus

Differential Revision: https://secure.phabricator.com/D9440