moving mail processor to module

fixes CNVS-12174

Test Plan:
Regression test on incoming mail.

Change-Id: I3f5d131ce4a1f4408bf95a5455ffc4baa6bdc85c
Reviewed-on: https://gerrit.instructure.com/32716
Reviewed-by: Braden Anderson <banderson@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Joel Hough <joel@instructure.com>