title: How to apply the same theme in all WPF windows using MahApps.Metro
body: <p>I'm newer with WPF projects and I have a question about the component MahApps.Metro.
  I created a MainWindow and other windows in my project, my question is: How to apply the same theme in MainWindow to the others windows of the project? And, I must to apply the ResourceDictionary for all windows or exist any way to do this one time only?</p>
  
  <p>Thank you guys!</p>