Beaten Transactions inputs, which may be unspent if the beaten spender loses, will no longer appear in any getUTXOs call.

[kayabaNerve]

First detailed in #292.

The reason for this is unless the spender is pruned, which it won't be as long as it has a single Verification on chain, getUTXOs will detect its existence and say "has spender; spent". We need to track beaten transactions and add this exemption in response.