Support to display paginated update list

• Updates are now displayed in a window with controls at the bottom: < X >
  
• UpdateView is gone in favor of a general NSView. Your update views don't need to implement a dismiss action anymore since the window takes care of this.
• The WhatsNew API now exposes display methods to pass in multiple Updates at once.

Stable Swift 5 Release

v1.0.0

update Swift version in README