Update `centos.svg' design model used inside documentation manuals:
    
        - Make the logo protection area 115x50mm.
    
        - The left margin between protection and content area was reduced
          to 0.5mm width. It would be 0, but due The CentOS Symbol left
          corner, it is necessary to leave some rooom for it to be
          rendered inside the protection area. Otherwise the symbol corner
          wouldn't be sharped but cut differing so from other corners.
          
        - The right margin between protection and content area was reduced
          to coincide the 115mm width the protection area has now.
    
        - The top and bottom margins between protection area and content
          was set to 10mm.
    
        Observations:
        -------------
    
        Using a left margin, as I previously did, makes difficult to
        control the visual alignment of The CentOS Logo on different
        places. For example, you cannot remove the left margin set on the
        image using CSS.
    
        It is necessary to reach a convenction so the logo implementation
        can be used consistently through different situations. In the
        present commit, I reduced the left and right margins and control
        them using CSS, when possible. The top and bottom margins are kept
        inside the image as unchangable values.
    
        Another point to consider here is that, because top and bottom
        margins are part of The CentOS Logo image itself, they are
        proportional with the image itself. The bigger the image is, the
        bigger the top and bottom margins will be. 
        
        An acceptable proportion, for most cases, is that produced by
        images of `78' pixels height. This produces an image where The
        CentOS Symbol is `48' pixels height and The CentOS Type `24'
        pixels height. The separation between The CentOS Symbol and The
        CentOS Type is of `10' pixels width. The content top and bottom
        margins are `15' pixels height each.
    
        The protection area is used to define the image boundaries. For
        example, if the image boundary is 115x50mm the final image will be
        115x50mm too, once rendered.