Fix and refactor the announce_entry class
- Removed verified from torrent_handle dict to announce_entry as it's read-only.
- Changed source and send_stats to read_write properties.
- Switched trivial type properties to using read_only or read_write.
The flags supplied by libraries cannot be relied upon to be sane so
they all must be run through a parser to make sure search paths are
specified in the correct order.
Calum Lind