Commit dialog does not show contents of directory that is not versioned only the directory itself

Sometimes such directories may have too many files inside, e.g. Obj/ subdirectory with object files after compilation of C/C++ project. Unlikely user will want to add such directory and it's content. So unlikely user will want to see this garbage every time.

I think will be better to expand directory content when user checks such item, to show what's else will be committed.

The bigger problem here is qadd's use of this widget. The other day, I had a new directory and wanted to 'bzr add' a file in it but not the whole directory. I couldn't do it in qadd so I had to fall back to using the command line. :-(

So we need to let the user drill down into unversioned directories to select files to add. Within the directory, we could hide things matching the ignore mask by default.

The little problem here is bzr itself does not provide recursive info about unversioned directories. So we have to implement this ourselves.