Add commands for session state loading

[pyroscope]

To load injected session state from other hosts or instances, keeping all metadata intact.

• load.session = ‹metafile path or pattern› – Load item as found in files (path can be a pattern as usual, resume data files are expected under the metafile path as a prefix)
• load.session.normal – Force active state = 0
• load.session.start – Force active state = 1
• load.session.verbose, load.session.normal_verbose, load.session.start_verbose – variants with logging
• Call event.download.inserted_new or event.download.inserted_session or even both?
• Set d.tied_to_file to source metafile, and d.loaded_file to session metafile

[kannibalox]

Would this cause incorrect reporting for private torrents?