Adds multiple constraints on the layout of the receiving view or its subviews.

All constraints must involve only views that are within scope of the receiving view. Specifically, any views involved must be either the receiving view itself, or a subview of the receiving view. Constraints that are added to a view are said to be held by that view. The coordinate system used when evaluating each constraint is the coordinate system of the view that holds the constraint. When developing for iOS 8.0 or later, use the  class’s  method instead of calling the addConstraints: method directly. The  method automatically adds the constraints to the correct views.