Cleaning up and removing remnance of the notification system.

Cleaning up and removing remnance of the notification system.

* Source/DebuggerConnection.h: Removing dead _data and prefixing socket with an _
* Source/DebuggerConnection.m: Prefixing use of socket with underscore, removing notification registration, documenting delegate methods
* Source/SocketWrapper.m|h: Removing the definitions for the notification types as we no longer use them