u3d UGUI Super TreeView 分享， 5.5.4或更高可用
Features:
- Support 3 animation effects of TreeView expanding or collapsing: Immediate, Scale and Clip.
（It can expand items immediately, or expand items by modifing speed , or modifing lasting time.）
- Support item padding .
( It's easy to change the vertical distance between each item.）
- Support item indent.
( It's easy to change the horizontal indent of each child item relative to its parent. ）
- Support expanding or collapsing all items at once.
- Support expanding or collapsing the selected item.
- Support easy to add or delete item.
- Support item inserted before or after the selected item.
- Use pool to cache items and don't destroy items at runtime.
- Platform-independent and full C# source code provided.
- Easy to use and understand.
