GDA-5819

fix dimensions used for writing strings
APRES-196 allow to persist subdirectory

Now you can swap StoredMetadataEntry to PersistantMetadataEntry (sic)
and the directories are kept over restarts
TESTING: update testing classpath
Merge branch '8.36'
Merge branch 'master' of ssh://dasc-git.diamond.ac.uk/gda/gda-core