email-ext: Expose reply-to and attach-build-log.

Options are self-explanatory hopefully.

Change-Id: I928851ebdaeb75f785d990008792d6a9e72512e3
Reviewed-on: https://review.openstack.org/27965
Reviewed-by: Jesse Keating <jesse.keating@rackspace.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins