improve method "directory_listing"
improve method "directory_listing"

split long "spaghetti"-style method "directory_listing"  for make possibility to override getting of listing folder
vechorko/django-filer,civicresourcegroup/django-filer,vechorko/django-filer,vechorko/django-filer,civicresourcegroup/django-filer,civicresourcegroup/django-filer,civicresourcegroup/django-filer,vechorko/django-filer