Implemented a FlipView control.

Implemented a simple FlipView control based on the one in Windows Store Apps (Windows 8/RT Metro Apps).

Based on the Selector control (like it's W.S.A. counterpart) and uses the TransitioningContentControl at it's core.
![m2](https://f.cloud.github.com/assets/251501/558328/336a6e5e-c415-11e2-93d4-48ebd83ecab3.png)
![m1](https://f.cloud.github.com/assets/251501/558329/336ec6ca-c415-11e2-9c8d-e95f06ff040f.png)