fix pale colours and map driverless print options

Set *DefaultBRColorMode: None in the vendor PPD so every job sends
<</UseCIEColor false>>: Brother's Normal/Vivid modes enable the printer's
own CIE conversion, which washed the colours out.

Add six APPrinterPreset entries mapping print-color-mode and
print-quality from driverless (AirPrint/IPP) clients onto the Brother
device options; they use the notation CUPS generates itself (Apple
metadata as 'key value' pairs, PPD options as '*Name Value'), because
key=value strings are silently discarded. print-quality is 3/4/5.

Add the PRINTER_OPTIONS env var: whitespace-separated key=value pairs
applied as queue defaults on every start via lpadmin -o, validated
against the queue's PPD, with warnings instead of a failed startup.

Document all of it in the README. The VividNoCIE candidate was dropped
after test prints showed no difference from None. Archive the OpenSpec
change and sync the printserver/cups spec with the two new
requirements.

assets/Brother HL-4150CDN/ppd/BR4150_2.PPD

@@ -374,9 +374,12 @@ restore
 *CloseUI: *BRPrintQuality
 
 *% Color Mode Information ===============
+*% Modified by this repo (see README, "Changes to the vendor PPD"):
+*% - default switched from Normal to None: with UseCIEColor off the printer
+*%   skips its CIE conversion, which otherwise washes out the colours.
 *OpenUI *BRColorMode/Colour Mode: PickOne
 *OrderDependency: 131.0 AnySetup *BRColorMode
-*DefaultBRColorMode: Normal
+*DefaultBRColorMode: None
 *BRColorMode Normal/Normal: "
 	<</UseCIEColor true>>setpagedevice
 	<</BRColorMode 0>>setpagedevice
@@ -393,6 +396,48 @@ restore
 *End
 *CloseUI: *BRColorMode
 
+*% Added by this repo: presets mapping the IPP attributes of driverless
+*% (AirPrint/IPP Everywhere) clients onto the device options below. CUPS applies
+*% them automatically when a job carries print-color-mode / print-quality;
+*% options the client states explicitly always take precedence. Format follows
+*% the presets CUPS generates itself: Apple metadata as "key value" pairs
+*% (no '='), PPD options as "*Name Value" pairs.
+*APPrinterPreset ColorDraft/Colour, Draft: "
+  com.apple.print.preset.output-mode color
+  com.apple.print.preset.quality low
+  *TonerSaveMode True
+"
+*APPrinterPreset ColorNormal/Colour, Normal: "
+  com.apple.print.preset.output-mode color
+  com.apple.print.preset.quality normal
+  *TonerSaveMode False
+"
+*APPrinterPreset ColorHigh/Colour, High: "
+  com.apple.print.preset.output-mode color
+  com.apple.print.preset.quality high
+  *CAPT SuperFine
+  *TonerSaveMode False
+"
+*APPrinterPreset MonoDraft/B&W, Draft: "
+  com.apple.print.preset.output-mode monochrome
+  com.apple.print.preset.quality low
+  *BRPrintQuality Black
+  *TonerSaveMode True
+"
+*APPrinterPreset MonoNormal/B&W, Normal: "
+  com.apple.print.preset.output-mode monochrome
+  com.apple.print.preset.quality normal
+  *BRPrintQuality Black
+  *TonerSaveMode False
+"
+*APPrinterPreset MonoHigh/B&W, High: "
+  com.apple.print.preset.output-mode monochrome
+  com.apple.print.preset.quality high
+  *BRPrintQuality Black
+  *CAPT SuperFine
+  *TonerSaveMode False
+"
+
 *% Improve Gray Color Information ===============
 *OpenUI *BRImprovedGray/Improve Grey Colour: PickOne
 *OrderDependency: 132.0 AnySetup *BRImprovedGray