doc: Added CORS support to Aodh

[OpenStack Infra]

https://review.openstack.org/265342
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/aodh" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit ab70d21919464db0522b6ee82b9e18ad7aa72646
Author: Michael Krotscheck <email address hidden>
Date: Fri Jan 8 08:03:11 2016 -0800

    Added CORS support to Aodh

    This adds the CORS support middleware to Aodh, allowing a deployer
    to optionally configure rules under which a javascript client may
    break the single-origin policy and access the API directly.

    In previous patches, proper paste support for gabbi was added. This patch
    modifies the paste.ini file for both aodh and gabbi, adds the CORS
    configuration fixture to support unit tests, and adds CORS into configgen.

    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
    DocImpact: Add link to CORS configuration in admin cloud guide.

    Change-Id: I27673b8581069c9ef02525756d1079b3904d8349