Removed unused Socket::socket()
Removed unused UDTSocket::socket()
Removed some old TODOs
Introduced namespaces.h in cpp files

And switched from boost::function to std::function
UDT::epoll errors print warnings, but don't crash the program
Don't crash server upon a timer error, instead print a warning
Forgot const for exception class refs
TCPServer doesn't crash upon failed TCPClient creation
Don't crash ProxyServer upon ProxyClient ctor failure
Throw exception when socket dies