Change start page's samples list box to treeView

Added show samples in folder
![capture](https://cloud.githubusercontent.com/assets/8348435/4116505/c1009dda-3285-11e4-8b33-550f9b37465a.PNG)

Can we remove the following and use the ```WPF.FindUpward``` helper method (can't remember the exact name, but it is something like that).