Modernize .arcconfig.
Summary: There have been several changes to the .arcconfig file format since this repository was last updated. In addition, the PhutilLintEngine no longer exists.
Test Plan: Eyeball it.
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: epriestley, Korvin
Differential Revision: https://secure.phabricator.com/D9445