Add support for Winsor-Newton colors

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There're several Winsor-Newton charts:

http://www.winsornewton.com/resource-centre/colour-charts/

Artists Oil Colour Winton Oil Colour Griffin Alkyd Fast Drying Oil Colour Artisan Water Mixable Oil Colour Artists' Oilbar Artists Acrylic Colour Galeria Acrylic Colour Artists Water Colour Cotman Water Colour Designers Gouache Drawing Inks Calligraphy Inks

The colors have other information, such as Colour name, Colour code, Permanence Rating, Opacity and the ASTM rating.

[dblock]

There's also a "classic" oil chart, I didn't dig into how it differs from WN. Other oil color producers seem to follow it: http://www.oldholland.com/products/classic-oil-colours/classic-oil-colours-colour-chart/