WIP: files

include/CMakeLists.txt

include/caosdb/file_transmission/download_request_handler.h

include/caosdb/file_transmission/file_error.h

include/caosdb/file_transmission/file_lock.h

include/caosdb/file_transmission/file_reader.h

include/caosdb/file_transmission/file_writer.h

include/caosdb/file_transmission/upload_request_handler.h

src/CMakeLists.txt

src/caosdb/file_transmission/client.cpp

src/caosdb/file_transmission/download_request_handler.cpp

src/caosdb/file_transmission/file_reader.cpp

src/caosdb/file_transmission/file_writer.cpp

src/caosdb/file_transmission/upload_request_handler.cpp

src/caosdb/transaction.cpp

test/test_file_transmission.cpp