Update Themes default design models for CentOS distribution major
    release 5:
    
        - Remove =MAJOR_RELEASE= translation marker from herein. Different
          major releases of CentOS distribution could introduce changes on
          files that would be difficult to handle using a common design
          model directory structure for all major releases of CentOS
          distribution. Also, such schema doesn't display the changing
          nature that may occur from one major release to another.
    
        - Instead of using =MAJOR_RELEASE=, the major release number of
          CentOS distribution is explicitly written in design models.
    
        - One directory structure is created for each major relase of
          CentOS distribution individually in order to isolate image
          production among different major releases. This way, it is
          possible to handle file name variations introduced by new major
          releases independently and saftly.