Fixes make_rss guid failure with unicode.

- Fixes #2068
Entry update_using_map now has ignore_none kwarg.
Increased discover verbosity level on search.
Search plugin flexget_archive now produces sensible results.

- Does not create None fields, Fixes #2069
Fixed some issues with torrent_alive related to invalid ports.
Merge pull request #57 from andir/invalid_port

Fixed some issues with torrent_alive related to invalid ports.
Add docs for 'interval' values in schemas