moved Facebook code into gem

fixes: CNVS-12120

test plan:
- regression test facebook functionality

Change-Id: I041e726ee12f9eca8fc27ccdd049422073d1af15
Reviewed-on: https://gerrit.instructure.com/33595
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>