Update `identity' functionality:
    
        - Remove pre-rendition configuration script parsing from
          identity_render. Command-line options will be used instead, to
          control post-rendition and last-rendition actions.
    
        - Move identity_renderBase to identity_render and remove
          identity_renderBase.
    
        - Rename THEMEMODEL variable to FLAG_THEME_MODEL. Put its initial
          definition in identity.sh.