add example for get_next via broker, refactor

CMakeLists.txt

common/cpp/include/database/database.h

examples/CMakeLists.txt

examples/worker/CMakeLists.txt

examples/worker/getnext_broker/CMakeLists.txt

examples/worker/getnext_broker/CMakeLists_separate.in

examples/worker/getnext_broker/Makefile.in

examples/worker/getnext_broker/check_linux.sh

examples/worker/getnext_broker/check_windows.bat

examples/worker/getnext_broker/getnext_broker.cpp

tests/broker/get_next/check_linux.sh

tests/broker/get_next/check_windows.bat

tests/mongo_db/insert/cleanup_linux.sh

tests/mongo_db/insert/cleanup_windows.bat

tests/worker/folder_to_db/check_linux.sh

tests/worker/folder_to_db/check_windows.bat

...orker/next_multithread_broker/next_multithread_broker.cpp

worker/api/cpp/CMakeLists.txt

worker/tools/folder_to_db/src/folder_db_importer.cpp

worker/tools/folder_to_db/src/folder_db_importer.h