in order to improve support for Tor connections.
This makes it possible to establish a connection to an .onion domain by
manually setting host and port in the ConnectionConfiguration and
configuring a Socks5Proxy pointing to a Tor node.
Fixes SMACK-720.
Instead of extending SocketFactory, the proxy support classes now
implement ProxySocketConnection. This removes a lot of unnecessary
code.
Also re-enables proxy support, which was broken in previous versions
because none of extended SocketFactories did override
createSocket() (SMACK-683).