DUI: styling update

Styles updated according [LibraryVisualSpec](https://drive.google.com/folderview?id=0B15a1zl00aS-MGVqWHdlS2Rmdnc&usp=sharing_eil).
What has not done yet:
- Class buttons alignment;
- Transparent Scrollbar.

Reviewers
@Benglin, please take a look.