refactor and cleanup

CMakeLists.txt

include/upnp/mapping.h

include/upnp/upnp_context.h

include/upnp/upnp_thread_util.h

src/connectionmanager.cpp

src/fileutils.cpp

src/ip_utils.cpp

src/security/diffie-hellman.cpp

src/upnp/protocol/igd.cpp

src/upnp/protocol/igd.h

src/upnp/protocol/mapping.cpp

src/upnp/protocol/natpmp/nat_pmp.cpp

src/upnp/protocol/pupnp/pupnp.cpp

src/upnp/protocol/upnp_protocol.h

src/upnp/upnp_context.cpp

src/upnp/upnp_control.cpp