I looked through all of the code, and in addition to fixing the
described problem, the proper way to add/remove morphs is now much more
clear.  (I never was quite clear on the proper use of the various
'private' methods which were being called publicly everywhere).  

The provided SUnit test does a good job of exercising all common cases. 
It is possible that specific Morph subclasses have bugs in the way that
they override the add/remove protocol (a lot of code was touched, and
there were bugs before).  However, with the SUnit test to serve as
reference for the desired behavior/usage, any bugs that might still
exist (I didn't find any) will be easier to identify as such.

All in all, this is a large improvement.  Since this changeset touches
so many methods in Morph and its subclasses, it is prone to bit-rot.  We
should get it into the image ASAP.













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