Left menu as a Tree

As an administrator I'd like to have the main menu is a tree-like structure so that it's easy to find out what pages relate to what components.
The current structure should look like this:

Components
   |_Configuration (currently it's called Components)
   |_Permissions (currently Group Permissions)
JCommune
   |_Sections & Branches (currently it's called Sections)
Users
   |_Management (currently it's called Users)
   |_Banning
   |_Groups
   |_Ranks
Topic Types

While it's self explanatory what happens when you click on particular leaf, it's not that clear what happens when user instead of expanding the tree, clicks on its parent node. In the future a page with accommodated info from all the child leaves will be shown, but right now we don't have that amount of functionality, so an empty page should be shown.
Note, that nothing should happen with the tree when Admin clicks on the node - it should only be selected (and not expand). But when user double-clicks, the node should expand.