I have updated the Color Theory article

I have updated the Color Theory article (pp. 18–21) to include my findings on the default tone curve used in Adobe Lightroom. This is the mysterious, seldom-discussed transformation that is applied to the image in addition to the well-known gamma encoding. The reason I am studying color theory is to understand the meaning of the RGB readouts in Lightroom. It turns out that  we have understand more than just the traditional color-theory topics.  We need also to study some peculiarities of Lightroom.