nsort sorts namespaces and pages together

When nsort sorting option is switched on, namespaces and pages on the same index level are sorted together.
I use it with msort option as well.
Original behaviour sorted namespaces first and then sorted pages were added.
Maybe new sorting option can be added for this mode.
The item array has the entry: `$dir_or_file['type']`. 
The value of this entry may be equal to `d` (unfolded **d** irectory), `l`(directory, **l** oad content of directory later) or `f` (**f** ile). So you can check for `$dir_or_file['type'] != 'f'`. 

Hmm, I don't know how I can add commits to your fork. I think I will look how I can add some tests. I like to ensure that the way of handling empty folders is maintained.