[#2347] Add orig_files to core
Refactor and tidyup code in torrent.py
Fix mistake in convert_lt_files
[#2161] Save magnet torrent_info to 'copy of' location

When magnet metadata is received a torrent file will also be written
to 'copy of' location if requested.
Modified the code for saving torrent file to state in Torrent class for
use by TorrentManager.