refactor worker errors

common/cpp/include/common/error.h

common/cpp/include/common/io_error.h

worker/api/cpp/include/asapo_worker.h

worker/api/cpp/include/worker/data_broker.h

worker/api/cpp/include/worker/worker_error.h

worker/api/cpp/src/folder_data_broker.cpp

worker/api/cpp/src/server_data_broker.cpp

worker/api/cpp/unittests/test_folder_broker.cpp

worker/api/cpp/unittests/test_server_broker.cpp