Added SocketReactor & fixes

Sockets will immediately return fr::Socket::Status::Disconnected if an attempt to send/receive data is made whilst the connection is closed.

Added SocketReactor, which is effectively a little wrapper around fr::SocketSelector, but can automatically call a callback for a socket when data is received on it.

src/SSLSocket.cpp

@@ -65,6 +65,7 @@ namespace fr
 
             if(read == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY)
             {
+                is_connected = false;
                 return Socket::Status::Disconnected;
             }
             else if(read <= 0)