extract JSONToken gem

fixes: CNVS-11785

Test Plan:
Automated tests will check most of it.  Make sure Canvas is not broken.

Change-Id: I797a71b492a043fc7d14b88457842bbde4295bb2
Reviewed-on: https://gerrit.instructure.com/31719
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>