tree-based navigation of workspace, limit File Explorer to workspace root

[gurok]

There are many threads asking for some kind of tree-based navigation of a workspace, some of them suggesting elaborate XML schemas in the workspace file to support this. In lieu of this, please consider allowing us to limit the File Explorer pane for a workspace to the workspace root (as an option). In my opinion, this would go about 90% of the way to achieving what people want with a workspace treeview.