Add .gitignore for uk.ac.gda.core.test junit log files generated by ant.
It is better to put .gitignore entries into the project.
Restore NexusDataWriter (only) to point before merge from 8.38 to 8.40
Merge remote-tracking branch 'origin/gda-8.40' into gda-8.42
Merge remote-tracking branch 'origin/gda-8.42'