Add some .arclint configuration options for ArcanistJSHintLinter.

Summary:
Allow .jshintrc and .jshintignore paths to be passed to jshint.

Ref T2039.

Test Plan: Added the jshintrc and jshintignore keys to an .arclint file that was configured to use ArcanistJSHintLinter. Ran arc lint --trace and inspected the flags that were passed to jshint.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: john.snow, epriestley, Korvin

Maniphest Tasks: T2039, T5085

Differential Revision: https://secure.phabricator.com/D9112