Dali store can get into a corrupt state, if out of disk during saving of new version

Whilst saving the store, a full disk exception can be hit during the file io dtors.
In that case, it will report the exception (log) but carry on (in jfile) to avoid crashing from throwing an exception in a dtor.
Dali being unaware, continues to put the new saved (truncated) store in place as the new store.

Change so that all save writes/closes are done 1st, before dtor's, thereby allowing the exception to be thrown, caught and handled.

That will result in the new store not being saved, which is 'ok', in the sense that the last store + delta will still exist for reload on the next start without any meta data loss.