https://developer.apple.com/library/mac/documentation/AppKit/Reference/NSLayoutConstraint_Class/
	https://developer.apple.com/documentation/uikit/nslayoutconstraint?language=objc
https://developer.apple.com/library/mac/documentation/UserExperience/Conceptual/AutolayoutPG/ProgrammaticallyCreatingConstraints.html#//apple_ref/doc/uid/TP40010853-CH16-SW1
	https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/AutolayoutPG/ProgrammaticallyCreatingConstraints.html#//apple_ref/doc/uid/TP40010853-CH16-SW1 (Listing 13-3)
https://developer.apple.com/library/mac/documentation/UserExperience/Conceptual/AutolayoutPG/WorkingwithScrollViews.html#//apple_ref/doc/uid/TP40010853-CH24-SW1
	https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/AutolayoutPG/WorkingwithScrollViews.html#//apple_ref/doc/uid/TP40010853-CH24-SW1 ("IMPORTANT Your layout must fully define..." large box)