added namespace to internal PixelRGB struct
added the following properties to allow customisation of colour wheel:
* clampRGBAmount, clampRGBMargin
* hueCount, hueOffset
* saturationCount, saturationMinimum, saturationMaximum
* knobBorderWidth, knobBorderColor
fixed issue with non-RGB color space models when setting the current color
added ability to swap the brightness and saturation of the colour wheel. when these values are swapped, adjusting the brightness property will adjust the saturation of the colour wheel