*colors module: move findColorName to a 'name' property on the RGB class.

*colors module: move findColorName  to a 'name' property on the RGB class.
*colors.RGB: add a 'fromString' factory method which creates an RGB instance from a CSS color string (such as rgb(x,y,z) or RGBA(x,y,z,w) or #XYZ or #XXYYZZ etc).
*colors.RGB: add a 'fromCOLORREF" factory method which creates an RGB instance from a COLORREF ctypes instance.
*IAccessible2 and soffice code: convert to use the new methods on the colors.RGB class.
*speech.getFormatFieldSpeech: allow color and background-color to be strings, as well as RGB instances.