Provide SSL information to Interceptor

[My original need](https://community.jboss.org/thread/234892) is to be able to identify message producer according to it's certificate.
I'm doing it using an interceptor and setting a property to each message received.

With the actual NettyConnection it's impossible to get any SSL related information so I added a getter.

Possible improvement : 
- Resolve a complete different way to achieve it because interceptor are called for ALL message type.
- return more or less information (SSLEngine, Certificate chain...)
- Add this getter into Connection interface. 

*Note: I found out using ChannelPipeline.get(Class<T> handlerType) was better than ChannelPipeline.get(String name) so I've also edited NettyConnection.close() method.*

Here is what my interceptor looks like : 

```Java
public class HornetQInterceptor implements Interceptor{

	Logger log = Logger.getLogger(HornetQInterceptor.class);

	public boolean intercept(Packet msg, RemotingConnection con)
			throws HornetQException {
		
		if(msg instanceof SessionSendMessage){
			SSLSession sslSession = ((NettyConnection)con.getTransportConnection()).getSSLSession();
			if(sslSession != null)
				try {
					((SessionSendMessage)msg).getMessage().putStringProperty("client.auth.dn", sslSession.getPeerCertificateChain()[0].getSubjectDN().getName());
				} catch (SSLPeerUnverifiedException e) {
					log.error(e.getMessage() + " Is NettyAcceptor's param need-client-auth set to true ?");
				}
		}
		return true;
	}
}
```