Adjust automatic markings on discrete knob when min and max change.
Added fillColorForState: and titleColorForState: (and related setters).
UIControlStateSelected can only occur programmatically, but we shouldn’t blow up if it does. Use the same colors as the UIControlStateHighlighted.
Added currentFillColor, currentImage, currentTitleColor (following the example of UIButton).
Adjust some more title colors.