SCDO initial release

In this initial release:

1. ZPoW phase 1: a new PoW consensus algorithm utilizing the properties of random matrices;
2. sharding protocol: the accounts, blockchain states are partitioned into different shards but can communicate with this secure protocol;
3. SCDO peer-to-peer protocol: the protocol for the communication of SCDO nodes;
4. support for smart contracts and decentralized applications: the virtual machine for smart contract execution is compatible with the Istanbul version of EVM;
5. JSON-RPC and client APIs for account management, getting data from the blockchain states, sending transactions, and developing applications.