Changes in my fork

[xyc0815]

@tayler6000 thank you for trusting in me and giving me access to your project.
I maybe my goals and your goals are same. In my fork I've done some changes that works fine for me and I think they will work also for you. Here is a birdview of my changes:

• I use this client for connections with an online service.
• I add a proxy for connecting an online service via a proxy. The proxy is in the moment only address and port.
• I changed the class VoIPCall. I use now the connection informations from VoIPPhone and don't transfer the values via initial call
• In the class SIPMessage I changed some function an also add a IPv6 support.
• In the class SIPClient I changed some connection values and message functions and I add the functions to use the Notification message
• I also add the Notification function to keep alive the connection to the server and not only a thread, this is only experimental in the moment
• In some parsing steps I add some fixes.
• In the class RTPClient I add some IPv6 support
• I've added a deeper logging for better analysing errors

I hope don't forget something important. I've merge your last changes in my fork. My next steps will be:

• Add a class for the connection information for a better overview of the connections in use and a better integration of IPv6
• Harden the made changes, in some cases they are only hotfixes.
• Search for fixes when running on errors.

The longtime goal for me is to add mircosoft speech services to this client. Maybe you can have a look on my fork to find out, what is good for your branch.

Regards xyc0815