Add folder view as file list with subfolder opening

[timbl]

The only current folder view has a nested set of folders but no attributes about the files.

User story: The user is able to switch the folder view, for one folder, or for all by default, to the one like Mac OS X does in: https://user-images.githubusercontent.com/1254848/76578094-dab29080-649d-11ea-8291-4a3a1c96f252.png

Users have complained that they would prefer other views, though we have no had survey of which they would prefer. Obviously views similar to those in the file browsers in OS X and Windows and various unixes would make sense.

This feature would find this widget useful: https://github.com/solid/solid-ui/issues/252