Write inititializations in topological order

Add methods to various places in the hierarchy so that the generator can
access the topologically ordered class list (in addition to the
unordered class list). Modify CppGenerator::finishGeneration to use
this.

This fixes a failure to correctly create Python wrapper classes due to
subclass wrappers being initialized before their base class (with the
result that the looked-up type object for the base class is null,
causing the derived class to be created without referencing the base).
Also change one of the test cases to test that we correctly wrap a
typedef of a template class derived from a non-template base (which was
failing before this change for the aforementioned reason).

Change-Id: Ib4dc2626a41cb7bb905ff4a302c2613ea12d026b
Reviewed-by: John Cummings <jcummings2@users.sf.net>