[Printing-architecture] Common Printing Dialog: PPD extension specs updated

[Till Kamppeter]

Hi,

after the conference call last week with Peter Sikking and the two GSoC 
students implementing the dialog and after some discussion with Mike 
Sweet from CUPS I have updated the specs of the PPD extensions:

http://www.linuxfoundation.org/en/OpenPrinting/PPDExtensions

I have done the following changes:

- Replaced the "*OPQuickPresets" keyword by "*APPrinterPreset" as
   defined in the CUPS PPD extensions on
   http://www.cups.org/documentation.php/spec-ppd.html#APPrinterPreset

- Mentioned that UI texts of PPDs should not be too long due to limited
   space in the dialog.

- Mentioned that a PPD cannot have more that 11 tags.

- Allow tags for options which are not in the PPD (like CUPS options)

- Allow canceling tags (like the predefined tags coming from CUPS
   options).

- Added section about CUPS options and their pre-defined tags

- Added new "donthide1choice" widget hint to not suppress an option
   when it has only one choice.

I appreciate very much your comments, especially about the tags for the 
CUPS options and additional document types for the "*APPrinterPreset" 
keyword.

I think with these extensions we should be well approaching the final 
specs for the PPD extensions.

    Till