This adds the CORS support middleware to Solum, allowing a deployer
to optionally configure rules under which a javascript client may
break the single-origin policy and access the API directly.
For solum, the middleware was added directly to the application
factory, including various default headers usually required by
keystone. Note that the CORS middleware must be the first one in
the middleware chain, so that it can annotate all responses -
even error responses - generated by other middleware.
Smoke tests have also been provided, and the middleware has
been added to genconfig.
OpenStack CrossProject Spec:
http://specs.openstack.org/openstack/openstack-specs/specs/cors-support.html
Oslo_Middleware Docs:
http://docs.openstack.org/developer/oslo.middleware/cors.html
OpenStack Cloud Admin Guide:
http://docs.openstack.org/admin-guide-cloud/cross_project_cors.html
Change-Id: Ie6bf73ea69ae956e9afe25ceca417c3a32edc312
82965f4bcb