Added MqttClientSslChannel and MqttServerSslChannel which both utilize
an SSL stream. Added options to both MqttCLientOptions and
MqttServerOptions. I was unable to update the code in
MQTTnet.UniversalWindows due to my lack of Windows 10.
* [Server] Fixed an issue with not correctly removed old client sessions.
* [Server] Several minor performance improvements.
* [Server] An existing client session is no longer closed if a new client connection is invalid.
* [Client] Added support for sending "CleanSession" flag.
Zazzmatazz
Christian Kratky