Add support for ColorBlock to the Odin Color Palette attribute.

[Joseph Fernald]

Unity has an internal variable called ColorBlock which is used for many of the GUI elements transition parameters, such as button, slider, check box and so on. The color block contains 4 colors (Normal, Highlighted, Pressed, Disabled) and 2 floats (Color Multiplier and fade duration).

It would be nice if the Color Palette Attribute could be extended to support this class as it would allow you to use the palette to determine these colors while staying "Themed".