Initial work on #789
Fixed the frame's built-in navigation UI's visibility.
Updated the InterestingPage.xaml and implemented more things in MetroNavigationWindow. Updated the default layout of the MetroNavigationwindow with a Glow and some margins around the frame.
Tweaks to the navigation demo: added a title. Added an opt-in "feature" for applying the clean style to the navigation window.
Updated documentation.
Documentation and event implementation.
Forgot to implement FragmentNavigation. Also fixed the documentation.
Added BackStack, ForwardStack and RemoveJournalEntry.
Added a Forward Button.
Renamed MetroWindowDialogExtensions to DialogManager. Those who use the extension methods correctly will not be affected.

Implemented the basic mechanics to show a dialog outside of a metro window.
Fixed the .NET 4.5 csproj file.
Fixed the height of external dialogs.
ProgressBar in the ProgressDialog uses the AccentColor by default.
Changed External Dialog methods into Extension Methods. External Dialogs use MetroWindows internally.
External dialogs fire OnShown and try to copy the dialog control's background.
Fixed the ProgressDialog's ProgressBar Foreground color when the Accent color scheme is used.
Internal dialogs can no longer be larger than their containing window. They will also have SizeToContent="Height" set.
Began implementing an event that fires when a dialog is shown/closed. Also implemented OnShown/OnClose for Simple/BaseMetroDialogs.
Initial animations support implemented.
ProgressDialog support for animations. MessageDialog support was added in the previous commit.