Issue #302 - fix bug in not showing 'next' button after delete
Issue #302 - change way row index is computed
Issue #211 - restore order of questionGroups in case something goes wrong
Issue #211 - restore order if things go wrong

Because of the high-replication datastore and possibly other
issues, sometimes the order of questions and question groups goes
wrong. Here, we check and correct it at each save.
Issue #211 - enable copying of questions across question groups