Support CrosschainLog

[quantumagi]

Adds ability to Interflux to incorporate destination account and network from a CrosschainLog. SC usage is as follows:

    public void MintWithMetadataForNetwork(Address account, UInt256 amount, string metadata, string destinationAccount, string destinationNetwork)
    {
        MintWithMetadata(account, amount, metadata);

        // Perform a cross-chain transfer.
        if (TransferFrom(account, Interflux, amount))
        {
            Log(new CrosschainLog()
            {
                Address = destinationAccount,
                Network = destinationNetwork
            });
        }
    }

[zeptin]

This looks good, but maybe the changes from #1145 should be incorporated into it as well, as there is some overlap.