restructured io files

common/cpp/include/common/io_error.h

common/cpp/include/io/io.h

common/cpp/include/io/io_factory.h

common/cpp/include/unittests/MockIO.h

common/cpp/src/json_parser/rapid_json.cpp

common/cpp/src/json_parser/rapid_json.h

common/cpp/src/system_io/io_factory.cpp

common/cpp/src/system_io/system_io.cpp

common/cpp/src/system_io/system_io.h

common/cpp/src/system_io/system_io_linux.cpp

producer/api/include/hidra2_producer.h

producer/api/src/producer_impl.cpp

producer/api/src/producer_impl.h

producer/api/unittests/test_producer_impl.cpp

receiver/src/connection.cpp

receiver/src/connection.h

receiver/src/receiver.cpp

receiver/src/request.cpp

receiver/src/request.h

receiver/src/request_handler_file_write.cpp