added Image UIElement

Example usage:

```c++
mTutorial1->addImage( "Two Hands", loadImage( loadResource( TWO_HANDS_IMG ) ), "{ \"clear\":false }" );
```

In context:

![2014-05-08 08 35 56 am](https://cloud.githubusercontent.com/assets/1994207/2915434/5a82cbb6-d6ad-11e3-8546-51ce6fca4dff.png)