[XNIO-196] Add first handshake handling to SSL conduits setTLS (this makes sure the read/write listener is invoked when SSL_STARTTLS is true and tls is enabled).

Also:
- add SSL connection/channel tests with the SSL_STARTTLS option enabled
- fix close mechanisms in SSL connection.
Improve workaround to bug found in SSLEngine. Update tests accordingly.
Javadoc
Add support for simple token-based connection balancing