Added CDiffProvider to provide proper CDiff instance based on context (height and net type -- testnet or mainnet)
Extra debug information in CDiff implementations
Fixed bnProofOfWork init. in CDiff class
Fixed COldNetDiff::ComputeMinWork() : invalid formula causing valid blocks to be rejected (too little POW)
Fixed getnetworkhashps (invalid arg type when called using [blocks] param from CLI) and adjusted CDiffProvider branch condition
Merge pull request #7 from ftcminer/Testing

Testing -- implemented oatmo's suggested refactoring