Move google_docs code into a gem

fixes: CNVS-12329

Change-Id: I044725c93582cbca39a61e036bb5f0385e069c1e
Reviewed-on: https://gerrit.instructure.com/32990
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>