Add Rnotes directory structures:
- Add trunk/Identity/Models/Tpl/Rnotes. This directory contains
the release notes design templates in docbook format.
- Add trunk/Locales/Identity/Models/Tpl/Rnotes. This directory
contains the release notes translation messages in PO format.
- Add trunk/Identity/Models/Img/Rnotes. This directory contains
the final release notes files in XHTML and plain-text format.
Files in this directory are used by `centos-release-notes'
package.