Adds an /xdomain_proxy.html endpoint that serves
the proxy file from the xdomain library. This
allows IE9 users to iframe in the proxy page
to simulate a cross-domain request with cookies.
xblock-external-ui: Alternate referer check for CORS requests
xblock-external-ui: Allow to disable httponly on session cookies
xblock-external-ui: Add a unit test for CorsCSRFMiddleware