replace ComputeMinWork with CheckMinWork
Remove redundant pblock->nNonce = 0
Move UpdateTime to pow
Rejected: Remove miner optimization
CBlockIndex()::SetNull() method to avoid code repetition
Use GetBlockTime() more
Encapsulate CBlockHeader fields for pow checks
Encapsulate CBlockHeader fields for pow updates
Proof abstract class
Proof: Cast to ProofOfWork for outputs
Proof::ToString()
FIXME serialize
FIXME tests
FIXME nonce in miner
FIXME CBlockIndex::GetBlockWork()