Report when Relationship TargetDAOKey not found

[jlhughes]

The Relationship TargeDAOKey, when not explicitly specified, is calculated based on the target property. If this is incorrect, then a NullPointerException is generated when the missing TargetDAO is referenced. We know when this occurs so add reporting/logging.

[kgrgreer]

The following commit adds one check, but there are several other places that need similar support:

commit 4124b06 (HEAD -> master, origin/master, origin/HEAD)
Author: Kevin Greer kgrgreer@gmail.com
Date: Fri Feb 22 10:58:00 2019 -0500

Add assert that targetDAOKey is present.