Move `render_doPostActions.sh' to `Backends/Svg/svg_commandPngTo':
    
        - It is not convenient to load `render_doPostAction' functionality
          inside SVG post-rendition functionality. The RENDER_BACKEND is
          used as suffix to execute functionalities and `render_' doesn't
          coincide with it. This way, move the functionality into SVG
          backend to make it loadable.
    
        - In this configuration, it seems to be no viable design to have
          one common post-rendition function that severs as model to all
          backends.  So, each backend should have its on implementation
          post-rendition models.