Completed tests and nearly finished merging

common/cpp/include/system_wrappers/io.h

common/cpp/include/system_wrappers/system_io.h

common/cpp/src/system_io.cpp

common/cpp/src/system_io_linux.cpp

common/cpp/unittests/MockIO.h

examples/producer/dummy-data-producer/CMakeLists.txt

...ples/producer/dummy-data-producer/dummy_data_producer.cpp

producer/CMakeLists.txt

producer/api/src/producer.cpp

producer/api/src/producer_impl.cpp

producer/api/unittests/test_producer_impl.cpp

receiver/src/network_producer_peer.cpp

receiver/src/network_producer_peer_handlers.cpp

receiver/src/receiver.cpp

worker/api/cpp/unittests/test_folder_broker.cpp