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)

Next time please remember to use ```var subProperty``` instead of ```SampleFileEntry subProperty``` since the type is known. But that's for next time.