cleanup & fix various bugs. hkey is now HKCU, no longer HKLM.
TODO: use advanced ASSERT-s later
in case of an exception, show a message box!
fix various bugs.
Socket::InitSockets must throw. TODO: later, I should change it so it returns void.
fix bug appearing in refactoring: only one socket and only one server must be created.
fix various bugs. put back mistakenly deleted function (now named, ServerConnThreadProc)
change Thread usage mode: no longer pass a ptr to function. Now each thread must have its own class, inheirt Thread, and implement OnStart()
Add HandshakeThread: will replace the Handshake function (called in different thread) in DataTransferer; Recv will be replaced with ReceiveFilesThread: now a thread. The same with SendFilesThread.