set x-canvas-meta response header

Include relevant request information, for easy storing in web access
logs

closes CNVS-11044

test plan: Make web requests, use your browser's web inspector to verify
the x-canvas-meta response header.

Change-Id: I07e31b571bd9a946c9bc753c60eb8872ff456ff7
Reviewed-on: https://gerrit.instructure.com/37276
Product-Review: Brian Palmer <brianp@instructure.com>
QA-Review: Brian Palmer <brianp@instructure.com>
Tested-by: Brian Palmer <brianp@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>