OVM Plasma Gametree Sequence (WIP)
1. detect exit claim which isn't true by OVM decider
2. client(guard feature) calls UAC.claimProperty(counterClaim).
3. client calls UAC.challenge(exitClaim, counterClaim).
4. client calls Predicate.decideTrue(counterClaim.inputs, /*witness if needed*/).
5. client calls UAC.decideClaimToFalse(exitClaim, counterClaim).