JSON array with null or undefined value will now skip the offending item, and proceed to load following items. Added tests for null and undefined array elements.
* Testing handling null and undefined id in block definition.
* Adding test utility function to capture console warnings.
* Test assumption that creating a simple block will not cause a warning. This is assumed when later checking warning counts.
* Beginnings of a JSON block definition unit test set.
* Dispose of unit test workspaces and blocks in finally blocks.
* Clarify JSON error message by echoing arg notation.