Project loading backwards-compatibility after compiler update

[cpdt]

The compiler update resulted in a few project format changes that need migrations in place:

• NumValues no longer have an active property, so this should be ignored in older projects.
• History action for setting code has changed, previously it was a CompositeAction containing a SetCodeAction and several control creation/deletion actions - now it is a SetCodeAction which contains those control creation/deletion actions inside.

#35 would be useful to aid history migrations in the future, too.