title: Making a button persistent across all view controllers
body: <p>I want to have a persistent button in the bottom right corner of my app.  During all view transitions, the button should remain static.  I'm having trouble deciding what view to add the button to.  I know the button ought to be stored in the AppDelegate, but I don't know what other view it would be sense to add it to except the window.  One downside of adding it to the window is that when there's an app running in the background (ie Phone), the added status bar padding will push down the window.  In general, adding it to the window seems to be a hacky solution -- any thoughts?</p>