MAINT: refactor logging (remove boost.log from headers)

CMakeLists.txt

include/CMakeLists.txt

include/caosdb/certificate_provider.h

include/caosdb/configuration.h

include/caosdb/entity.h

include/caosdb/file_descriptor.h

include/caosdb/file_transmission/download_request_handler.h

include/caosdb/file_transmission/file_reader.h

include/caosdb/file_transmission/upload_request_handler.h

include/caosdb/logging.h

include/caosdb/transaction.h

src/caosdb/configuration.cpp

src/caosdb/entity.cpp

src/caosdb/file_transmission/download_request_handler.cpp

...caosdb/file_transmission/register_file_upload_handler.cpp

src/caosdb/file_transmission/upload_request_handler.cpp

src/caosdb/logging.cpp

src/caosdb/transaction.cpp

src/caosdb/transaction_handler.cpp

src/caosdb/unary_rpc_handler.cpp