idgames_db_dump.ini: fixed incorrect file purpose in comments
іndex.ini: fixed tool used for file in file comments
renamed: index.ini -> wad_index.ini
wadindex: clarified output in log messages
Database: issue #87: unserialize_file() is working now

- Return 'undef' from get_file_by_path() if the database query returns
  no rows (usually this happens when querying for text files)
- Added more debug logging