Add optional colord support to the CUPS print module

Add optional colord support to the CUPS print module

This functionality adds a new 'Printer Profile' entry to the 'Color' page in the
UNIX print dialog if colord support is enabled.

This shows the user what color profile will be used for the settings they have
selected, and if no profile or the default profile is going to be used.

We are deliberately not allowing the user to _change_ the selected profile, as
the ICC profile is an implementation detail, and we should not change the other
print settings based on the characterization state.

The OpenICC group broadly recommend showing the profile that is used, so that
power users can be sure the correct profile is being used at the right time.

Normal users won't care, as they don't know how horrible the color match is
without profiling the printer and media.