[PWG5100.13] Issue #135: 6.2.3 print-color-mode (type2 keyword) - support non-black monochrome non-black printers

[Issue Unconfirmed]

CMY only printers aren't clearly discussed in 6.2.3, nor is the meaning of
'monochrome' when the printer has one marking agent that is NOT black.
Consider these issues and expand the definition in a way that is backwards
compatible.

Link: http://www.pwg.org/issues/135