huey: Internal maintenance specification

Similar to Section 20.2, “Swatch.setTextColor()”, but the background color is the "bg" attribute.

# - - -   S w a t c h . s e t B g C o l o r

    def setBgColor ( self, color ):
        """Sets the background color of self.__text.
        """
        self.__text["bg"]  =  str(color)