- Clarify "tunnel_changed" event documentation.
- Make expiration of "Tunnel::active" elements configuration via
"Tunnel::expiration_interval".
- Remove redundant registration of a connection's tunnels in
tunnel/main.bro's "tunnel_changed" handler.
- Rename "parents" field of "Conn::Info" to "tunnel_parents"
to give more context.
conn.log now sets a field indicating all the parent tunnel UIDs over
which a connection operated and cross reference the UIDs found in
the tunnel.log.
Also some renaming of tunnel related types at the scripting layer.
