Adding a test to ensure handling null correctly.  It currently fails.
Minor bug: called wrong super type for null node in parser.
Emitting for null types.  Causes error in test.  Check that it works still.
To acommodate nulls, check whether using null before copying it.
Increased coverage of null tests to also apply to strings and true falses.
Expanded null test to test more sets and gets.
Updated emitter to support null map and list initializations.
Updated null test to test for nulls in maps.
Prevents null pointer exceptiosn when testing equality for null objects.
Extended null tests to test for equality.