public GrProperty addProperty(String name, Object value) {
		GrProperty prop = GrAccess.createProperty(name);
		prop.setValue(value);
		return getPropertiesContainer().addElement(prop);
	}
public GrProperty addProperty ( String name , Object value ) { GrProperty prop = GrAccess . createProperty ( name ) ; prop . setValue ( value ) ; return getPropertiesContainer ( ) . addElement ( prop ) ; }
add a new property, throw a RuntimeException if the property already exists
@param name of the property
@param value of the property
@return the added property