more colors purged from studio palette

I will probably keep an ultramarine just for mixing darks, following Liz Steel's suggestion. It costs less than cobalt.

When the payne's gray and lunar blue are gone, I may not replace them. Not sure. And when the cadmium orange is gone, I will try Liz' suggested Schmincke transparent orange instead. Cadmium paints don't always play well with others.

Meanwhile, the cobalt turquoise and potter's pink are only included as fun trials.