Store contents (list) of archive files in filebase (in the "msg tail")
This will allow fast/easy display of archive contents without actually reading the archive files. Introduces some new functions: - list_archive_contents() - smb_adddfile_withlist() A new SMB convenience variable ("tail", aliased as "content" for a file). A new file detail level ("file_detail_content", exposed in JS as FileBase.DETAIL.CONTENTS) which adds a "content" array property to file metadata objects for JS FileBase.get(). Files already added to the new filebases won't have this archive content automatically - I'm looking into that now (likely a new or updated JS script to run).