Change "ofp.open" to "ofp.listen", initial support for conn id's.

Replace Driver::Role by ChannelMode enum.
Replace ofp.open by ofp.listen.
Add localEndpoint() abstract method to Channel.
ofp::log() supports std::pair and std::error_code.
Add support for UInt64 connection ID’s to Engine in registerServer.
Remove Server class and include/ofp/server.h
UDP_Server is created as a child object of TCP_Server so it will have
the same connection ID.