title: PRISM creates new ViewModel by each navigation request?
body: <p>I am using Prism v6.3.0 for a UWP app. I am using the Unity Container for DI.
  Following problem occurs: whenever my app navigates to a given view (e.g. MainPage) there seems that a new instance of the corresponding ViewModel is created. I would like to reuse the same VM (basically, to have it only once created).<br />
  I am having: <code>prismMvvm:ViewModelLocator.AutoWireViewModel=&quot;True&quot;</code> in all of the pages' XAML.<br />
  My code never calls directly any VM constructor, so it cannot be that. I am also registering only services in the ConfigureContainer override.</p>
  <p>What I've tried is to register the Views in App.xaml.cs (it seems to make no difference):</p>
  <pre><code>private void RegisterViews()
  {
          Container.RegisterInstance(new LoginPage(), new ContainerControlledLifetimeManager());
          Container.RegisterInstance(new SettingsPage(), new ContainerControlledLifetimeManager());
          Container.RegisterInstance(new MainPage(), new ContainerControlledLifetimeManager());
  }
  </code></pre>
  <hr />
  <p>Any hints?</p>