Init virtual sub-directory name for library sub-dirs

When using the "Access to Sub-directories" option for a library, the auto-created directories did not have their virtual sub-directory name set. Pretty sure this was introduced along with the http access to filebases after v3.19b.

Also, only de-dupe the sub-directory names based on the directory name and not the code/code-suffix for now. Next up: auto-gen unique internal code when needed.