* common/TypeNode.h, common/TypeNode.cpp: Move TypeNode into
its own files.
* common/Makefile.am, common/inheritance.cpp, common/inheritance.h:
Add the new files to the build and remove the old implementation.
* client/Py_CreatorClient.cpp, rulesets/Character.cpp,
rulesets/Entity.cpp, rulesets/MemMap.cpp,
rulesets/MindFactory.cpp, rulesets/Py_Mind.cpp,
rulesets/Py_Thing.cpp, rulesets/Stackable.cpp,
server/WorldRouter.cpp: Fix up the includes for all code that
uses TypeNode.