provide multibyte aware helper functions mb_str_replace, mb_substr_replace and mb_array_change_key_case for handling with UTF 8

- when creating a new text file or directory which name already exist use the same pattern as for file uploads in such a case (add a (N) to the name)
- don't allow renaming if a file/directory with the name already exists

do not create a db if already existing .. and reset the user password instead of creating if the user already exists