Merge branch 'f-files' into f-consolidation

src/caosdb/file_transmission/file_reader.cpp

src/caosdb/file_transmission/file_writer.cpp

...caosdb/file_transmission/register_file_upload_handler.cpp

src/caosdb/file_transmission/upload_request_handler.cpp

src/caosdb/transaction.cpp

src/caosdb/transaction_handler.cpp

src/caosdb/unary_rpc_handler.cpp

test/test_file_transmission.cpp