Update default design models for installation media at
    `trunk/Identity/Models/Themes/Default/Distro/5.5/Media':
    
        - Start using =RELEASE= translation marker.
    
        - Reorganize title centering it.
    
        - Remove symbols and types related to CentOS from installation
          media design models.
    
        - Add Creative Common Attribution-ShareAlike 3.0 License as
          default license used to release the work and print it near the
          copyright note.
    
        - Start using =COPYRIGHT_HOLDER= instead of `The CentOS Artwork
          SIG' string.