Start testing chaining proper
Replace the icky tree module. First step: redo the basic logic functions to work with pure Atoms
Remove use of tree class from chainer test
Change AbstractChainer to use Logic class
Make Chainer use Logic
Fix minor Python problem
fix things
Fix rules
Make PLN work
Experiment with PLN and ECAN
Don't allow silly results like 'a dog is a dog'
Added inference trail mechanism
Check for repeated inferences