title: Disable vibrancy for every NSView
body: <p>Inside an <code>NSPopover</code>, some subviews (e.g., labels, push buttons) have vibrancy enabled automatically. This makes my app looks very bad when the content behind the popover is in dark colors, unless the user turns on "reduce transparency" in System Preferences. If I subclass the content view of the popover, and set <code>allowsVibrancy</code> to false, it makes the entire popover translucent, which looks better. However, I think my app looks the best when vibrancy is disabled entirely.</p>
  
  <p>My question is, how do I disable vibrancy for all views, without subclassing each of <code>NSView</code> subclasses?</p>