Issue #1664940 by nod_, jibran, droplet | RobLoach: [Policy, patch] Decide on JSHint configuration.

Replacement PR for #318.

Drupal.org issue: https://drupal.org/node/1664940
And part of Backdrop issue: backdrop/backdrop-issues#211

As mentioned in #318, this differs from the D8 version in that we're placing these files within the /core directory, as this is only for linting core JS files and we can't predict which contrib/custom files should be ignored anyway.