Convert more linters to modern formats with .arclint support

Summary:
Ref T3186. Ref T2039.

• Convert JSHint to modern format; improve granularity of errors.
• Convert PyFlakes to modern format;
• Remove ApacheLicenseLinter and LicenseLinter (these have been deprecated for a very long time).

This is somewhat disruptive and will break some users by no longer respecting various path/config options. I'll sequence documentation and deprecation warnings in front of these.

Test Plan: Ran unit tests.

Reviewers: btrahan, Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: epriestley, Korvin, joshuaspence, aran

Maniphest Tasks: T3186, T2039

Differential Revision: https://secure.phabricator.com/D6810