Decorator base classes now have virtual methods
Moved all logic for determining default values into the runtime library
Allow a class in a plugin to implement more than one extensibility interface
Do not always ignore warnings about equality operators being defined but not Equals/GetHashCode
Use a local version of the QUnit import lib in the runtime solution.

This version is untested, may not be synced with the "real" QUnit lib, and should not be deployed. However, using the "real" QUnit lib causes ugly circular references which I consider worse than this option.
Re-added non-submoduled QUnit