Refresh the engine from the bytes given when an update from memory cannot write the data file #171

The errors table of data-updates.md (line 511 at 706de1f0) says that when "Writing data passed in from memory to the data file failed" it is logged as a Warning, "An error occurred when writing to '<path>'. The engine will be updated to use the new data but the file on disk will still contain old data.", and the Engine is still refreshed.

In 51degrees-python a failed write of a data file kept on disk ends update_from_memory with a DataUpdateException and the engine keeps its old data (#169), because the engines of data files kept on disk refresh by reading the file again.

Done when a failed write logs that warning and the engine is refreshed from the bytes given, with a test, red then green.