Draft: color-representation rewrite

Contains whole history and is not squashed down, so best way to view it is to look at the xml file at the HEAD.

Essentially a complete rewrite of the protocol:

• much closer in design to the color-management protocol
• color representation objects are immutable objects that can be set on surfaces
• color representation objects are created by a temporary creator object
• CICP code points are replaced with wayland enums
• everything is advertised
• arbitrary matrix coefficients for electrical and optical values can be set

Mostly looking for feedback before investing more time.

Still has rough edges:

• chroma_location enum is not implemented
• range enum is not is not implemented
• the interaction with pixel format channels (RGB, YCbCr, ...) is not defined
• ...