Switching to linear model
Fixed overloaded method, fixed obsolete test
Added CR ancestors map

Looked up on destroy
Almost complete

Need to figure out how to cleanly recursively purge PEs.
Indeed, PE's children don't know the State they're associated to, so we lack the key to purge them from states.
Modified children set to include a mapping to State

Also: Full engine test, fixed partial functions
Merge pull request #44 from Geogi/dev

Automaton engine: merged.