Merge branch 'f-files' into f-consolidation

include/CMakeLists.txt

include/caosdb/connection.h

include/caosdb/entity.h

include/caosdb/file_transmission/Client.h

include/caosdb/file_transmission/DownloadRequestHandler.h

include/caosdb/file_transmission/FileError.h

include/caosdb/file_transmission/FileLock.h

include/caosdb/file_transmission/FileReader.h

include/caosdb/file_transmission/FileWriter.h

include/caosdb/file_transmission/UploadRequestHandler.h

...e/caosdb/file_transmission/register_file_upload_handler.h

include/caosdb/handler_interface.h

include/caosdb/protobuf_helper.h

include/caosdb/status_code.h

include/caosdb/transaction.h

include/caosdb/transaction_handler.h

include/caosdb/transaction_status.h

include/caosdb/unary_rpc_handler.h

include/caosdb/utility.h

src/CMakeLists.txt