Sync neo

[bettybao1209]

Close #519

1. Needs to add a new message type GetInstance in LocalNode class;
2. UpdateExtensibleWitnessWhiteList in Blockchain class and Verify in ExtensiblePayload class should be public, since they are needed in DBFT plugin.
3. https://github.com/neo-project/neo/blob/master/src/neo/SmartContract/Native/LedgerContract.cs#L72 will throw NullReferenceException, which is caused by the non-existence of the CreateStorageKey(Prefix_CurrentBlock) (invoked before PostPersist).

[erikzhang]

Verify in ExtensiblePayload class should be public, since they are needed in DBFT plugin.

Why do you need Verify? The payloads are verified before you receive.

[erikzhang]

@bettybao1209 Can you fix the checks?

[cloud8little]

@Qiao-Jin and I Debug and find it failed in VerifyWitnesses.

https://github.com/neo-project/neo/blob/master/src/neo/Network/P2P/Payloads/ExtensiblePayload.cs#L98

        internal bool Verify(ProtocolSettings settings, DataCache snapshot, ISet<UInt160> extensibleWitnessWhiteList)
        {
            uint height = NativeContract.Ledger.CurrentIndex(snapshot);
            if (height < ValidBlockStart || height >= ValidBlockEnd) return false;
            if (!extensibleWitnessWhiteList.Contains(Sender)) return false;
            return this.VerifyWitnesses(settings, snapshot, 0_02000000);
        }

because it return false here:
https://github.com/neo-project/neo/blob/master/src/neo/SmartContract/Helper.cs#L235

                engine.LoadScript(invocationScript, configureState: p => p.CallFlags = CallFlags.None);

                if (engine.Execute() == VMState.FAULT) return false;
                if (!engine.ResultStack.Peek().GetBoolean()) return false;
                fee = engine.GasConsumed;

@erikzhang do you have any insight?

[erikzhang]

Please test it with neo-project/neo#2367.