create a spec for a variable store.
create the variable store.
avoid struct subclassing problematic in tests

You can get a superclass type mismatch in tests
in some cases, if you subclass from Struct.
ensure that as() in variable store returns self.
include variable store and test functionality

A 'Full-Stack-Test' should ensure functionality
of variable-assignment through the as() method.
create variable-store shorthand on object-def.
add tests for custom variable assignment.
Merge branch '2-custom_variables_on_ontology_object'