Graph rewrite.
Major reworking motivated by having an explicit representation for graphs.
Should have checked in before this--sorry.
Added pending/source attributes to variables.
Removed egraph since it's not working.
Refactoring.
Renaming test files
bugfix - fixing variable/function having same name
Forgot to delete this file.
New model builder
Took all builder logic out of model and put it into new ModelBuilder class.
Removing "shadow" graph functionality
Left it in an unused file: graph-cor.js
Variable.onNext guards against changes to the same value
Bugfix: fixed observers to prevent multiple updates
Memory cell example; async flag
Asynchronous notifications.
Another big change.  Sorry.
New test for exponential messages.
Slight change to logging