refactoring reciever

common/cpp/src/system_io/system_io_linux.cpp

receiver/CMakeLists.txt

receiver/src/connection.cpp

receiver/src/connection.h

receiver/src/main.cpp

receiver/src/network_producer_peer.cpp

receiver/src/network_producer_peer.h

receiver/src/network_producer_peer_impl_functions.cpp

receiver/src/network_producer_peer_impl_handlers.cpp

receiver/src/receiver.cpp

receiver/src/receiver.h

receiver/src/request.cpp

receiver/src/request.h

receiver/src/request_handler.cpp

receiver/src/request_handler.h

receiver/unittests/test_connection.cpp

receiver/unittests/test_network_producer_peer.cpp

receiver/unittests/test_receiver.cpp

receiver/unittests_OLD/test_file_reference_handler.cpp

receiver/unittests_OLD/test_receiver.cpp