Update trunk/Identity/Themes/Models/Default directory structure:
    
        - Sometimes, between major releases, image files inside packages
          can be added, removed or just change their names. In order to
          describe such image files variations, the design models
          directory structure is organized in the same way the file
          variations are introduced (i.e., through The CentOS Project
          Release Schema). So, each major release of CentOS Distribution
          does have its own design model directory structure in this
          directory.