Add File Tree browser in the Source Code view

Scenario

1. In FishEye: if you click on the arrow in front of a folder or a package this part gets expanded you without page refresh. When you click a file, the source code will be shown directly in the right side of the screen in Fisheye.
2. In Stash : For each selection in the file browsers there is a page refresh or site refresh and source code is not shown directly.

What nice to have

1. The same feature as FishEye which can give the user more user usability to view the files using the tree viewer