Update render_doIdentityImageGrub.sh. 
    
        - Previous to this commit only one splash.xpm.gz file was created.
          That unique file was created using Floyd-Steinberg dithering
          wich improves results for some images. In other cases we don't
          want to use dithering but the exact colors provided in the
          palette of colors only.
    
        - In this commit we keep using Floyd-Steinberg dithering and
          additionally configure the script to produce images without
          Floyd-Steinberg dithering so we can choose which result is best
          for using.