removed receiver tests

common/cpp/include/system_wrappers/io.h

common/cpp/include/system_wrappers/system_io.h

common/cpp/src/system_io_linux.cpp

common/cpp/unittests/MockIO.h

producer/dummy-event-detector-cpp/src/dummy_detector.cpp

receiver/src/file_reference_handler.cpp

receiver/src/main.cpp

receiver/src/receiver.cpp

receiver/src/receiver.h

receiver/unittests/test_file_reference_handler.cpp

receiver/unittests/test_receiver.cpp