Represents a true/false flag that is under user control and which can be interrogated by a call to Preferences

name a symbol, the formal name of the preference.
value a boolean, the current value
defaultValue the default value of the preference
helpString string or text, constituting the help message
localToProject boolean, whether each project holds its own version
categoryList list of categories under which to offer this
changeInformee whom, if anyone, to inform if the value changes:
changeSelector what selector to send to the changeInformee when the value changes

	change notification
	changeInformee changeInformee:changeSelector: notifyInformeeOfChange

	debugging
	printOn:

	initialization
	categoryList: name:defaultValue:helpString:localToProject:categoryList:changeInformee:changeSelector:

	local to project
	isProjectLocalString localToProject toggleProjectLocalness

	menu
	categoryList copyName helpString name offerPreferenceNameMenu:with:in:

	value
	defaultValue preferenceValue preferenceValue: rawValue: restoreDefaultValue togglePreferenceValue

	button	top
	representativeButtonWithColor:inPanel: Return a button that controls the setting of prefSymbol. It will keep up to date even if the preference value is changed in a different place
	tearOffButton Hand the user a button the can control this

	change notification	top
	changeInformee Answer the receiver's changeInformee
	changeInformee:changeSelector: Set the changeInformee and changeSelector as specified
	notifyInformeeOfChange If there is a changeInformee, notify her that I have changed value

	debugging	top
	printOn: Print a string decribing the receiver to the given stream

	initialization	top
	categoryList: Set the receiver's categoryList
	name:defaultValue:helpString:localToProject:categoryList:changeInformee:changeSelector: Initialize the preference from the given values. There is an extra tolerence here for the symbols #true, #false, and #nil, which are interpreted, when appropriate, as meaning true, false, and nil

	local to project	top
	isProjectLocalString Answer a string representing whether sym is a project-local preference or not
	localToProject Answer whether this preference is project-local
	toggleProjectLocalness Toggle whether the preference should be held project-by-project or globally

	menu	top
	categoryList Answer the categoryList
	copyName Copy the name of the given preference to the clipboard
	helpString Answer the help string provided for the receiver
	name Answer this preference's name
	offerPreferenceNameMenu:with:in: the user clicked on a preference name -- put up a menu

	value	top
	defaultValue Answer this preference's defaultValue
	preferenceValue Answer the current value of the preference
	preferenceValue: set the value as indicated, and invoke the change selector if appropriate
	rawValue: set the value as indicated, with no side effects
	restoreDefaultValue restore the default value to the preference
	togglePreferenceValue Toggle whether the value of the preference