All IG code should use the interface of LocatedEntity when dealing
with any entity, rather than sometimes requiring Entity. Add virtual
functions to the interface where required, and modify all other interfaces
to stop them using Entity. This makes the code way cleaner, and much better
de-coupled.
The Link reference provided is the object allowing direct communication
back to the external source of the operation. This allows us to handle
things more cleanly in some cases.
* tests/Entitytest.cpp: Update so that it no longer expects the
contains property to be set by default.
* tests/EntityReftest.cpp: Fix tests so that when calling destroy
on an Entity, it's hierarchy is as expected.
* modules/EntityRef.cpp, modules/EntityRef.h: Add a new class to handle
a weak reference to an Entity.
* tests/EntityReftest.cpp: Test the weak reference class.
