Add render_doIdentityImageGdm.sh (last-rendering) functionality to
    produce gdm tar.gz theme files for different artistic motifs and major
    releases of CentOS distribution.
    
    Update GDM render.conf.sh pre-rendering configuration script to use
    render_doIdentityImageGdm functionality as last-rendering action. In this
    commit, tar.gz files are produced for the following screen
    resolutions: 800x600 1024x768 1280x1024 1360x768 1680x1050 2048x1536
    2560x960 2560x1240 3271x1227.
    
    Replace `sanitize' word to `sanitate'.