Merge remote branch 'origin/feature/7228_ConverToMDPerformance'
Refs #8028 - Avoid dereferencing an end iterator.
Refs #8028 - Ensure map is being accessed at an existing key.

These changes pass the unit tests, but it would be good if someone who
knows more about this code could take a look to double check it works as
intended.
Refs #8028 - Pin down debug error with unit test.
Merge branch 'feature/8028_fix_windows_7_db_build' into develop