enhancement to fix #515 (flyouts and themes)

this pr fixes the #515 (listview on flyouts) and use always the dark theme to avoid strange coloring.

- [x] enhance flyout demo
- [x] let flyouts using the dark theme
- [x] Caliburn.Metro.Demo doesn't work :-( but i don't know why this doesn't work
- [x] some restyling flyouts
- [x] #679 Prevent user from closing Flyouts (using command)

![image](https://f.cloud.github.com/assets/658431/1352531/04f54890-3739-11e3-9c7b-1328da305229.png)
![image](https://f.cloud.github.com/assets/658431/1352538/073f3e12-3739-11e3-9448-6946319f3091.png)
![image](https://f.cloud.github.com/assets/658431/1352539/092d0718-3739-11e3-9069-1c30ae298e1e.png)
![image](https://f.cloud.github.com/assets/658431/1352540/0af211a6-3739-11e3-8d45-3cf7703f83a4.png)
![image](https://f.cloud.github.com/assets/658431/1352541/0cb0afd4-3739-11e3-97c1-4d0f49ae3412.png)
![image](https://f.cloud.github.com/assets/658431/1352542/0e7d17c6-3739-11e3-9a81-4abb56782626.png)


Closes #515 
Closes #679