refactor, added db import tool with tests, started class for mongodb

CMakeLists.txt

CMakeModules/testing_cpp.cmake

common/cpp/CMakeLists.txt

common/cpp/include/common/file_info.h

common/cpp/include/database/database.h

common/cpp/include/database/mongodb_client.h

common/cpp/include/system_wrappers/io.h

common/cpp/include/system_wrappers/system_io.h

common/cpp/include/unittests/MockIO.h

common/cpp/src/database/CMakeLists.txt

common/cpp/src/database/mongodb_client.cpp

common/cpp/src/system_io/CMakeLists.txt

common/cpp/src/system_io/system_io.cpp

common/cpp/src/system_io/system_io_linux.cpp

common/cpp/src/system_io/system_io_windows.cpp

common/cpp/unittests/test_common.cpp

examples/worker/process_folder/CMakeLists.txt

producer/api/CMakeLists.txt

tests/system_io/read_file_content/CMakeLists.txt

tests/system_io/read_files_in_folder/CMakeLists.txt