Add a navigation page

I added a navigation page. I have not finished yet. It is still ugly now
and I have not turn the game window into a page.
working on game pages

waiting to invoke game thread
finished basic game page frame

Waiting to invoke game engine;
One score Label in dual mode is misplaced...
poor navigation design... but it does work

To change the window size in some sepcific pages, I used "Callback" to
pass the window ref. It is really not a good idea. But I found no way
else.

And there are lots of parts in my code are duplicated... It is really
bad.

I will implement fade-in & fade-out appearance later.
Added fade-in & fade-out effect
Added some effect, not finished
Added a animation for a greeting message

poor design as usual..
Can play now
Add some background pictures and maximize the window
Extract the Navigating effect out of AdvancedGUI.MainWindow
Merge remote-tracking branch 'origin/AdvancedGUI' into gamelogic

Conflicts:
	Tetris/MainWindow.xaml.cs
Repair Merge Bugs