Add snapshot synchronization #23

Snapshot synchronization was originally almost implemented in CodeChain/snapshot branch.
The blocking problems were related to asset timelocks, and since we're stripping asset implementation in this repository, we just have to port the commits to this repository.

The following is the list of commits to be ported:

• CodeChain-io/codechain@18001f6 Introduce on_open_block Update tendermint implementation to be compatible with snapshot sync #27
• CodeChain-io/codechain@3c8d9f0 Implement TrieDB::is_complete Import the snapshot header #29
• CodeChain-io/codechain@1dff7e2 Add complete_register to ConsensusEngine Create snapshots #19
• CodeChain-io/codechain@fc6a3de Change waitNodeUntilTerm to return TermMetadata Refactoring patches from CodeChain/snapshot #22
• CodeChain-io/codechain@80e6282 Refactor rpc startup code Add RPCs for managing snapshots #20
• CodeChain-io/codechain@74c46d6 Refactor send status function Refactoring patches from CodeChain/snapshot #22
• CodeChain-io/codechain@ec0ef2b Remove unnecessary cloning in block sync Refactoring patches from CodeChain/snapshot #22
• CodeChain-io/codechain@06b3f97 Enhance error message in waitForTermChange Refactoring patches from CodeChain/snapshot #22
• CodeChain-io/codechain@3b9c388 Add term_params to Metadata Read term_common_params from the state #18
• CodeChain-io/codechain@5c64737 Snapshot term_metadata on every term close for the era > 0 Read term_common_params from the state #18
• CodeChain-io/codechain@7fba4f5 Update the era with the value in current block's state Not related
• CodeChain-io/codechain@9a6ec55 Read term_params from the snapshot Read term_common_params from the state #18
• CodeChain-io/codechain@1101c5b Precalculate the fee in era=1 Update tendermint implementation to be compatible with snapshot sync #27
• CodeChain-io/codechain@1051665 Remove outdated snapshot module Create snapshots #19
• CodeChain-io/codechain@f718e4a Add configuration option for the snapshot sync target Import the snapshot header #29
• CodeChain-io/codechain@b3e2238 Decide the sync extension's state with the snapshot target Import the snapshot header #29
• CodeChain-io/codechain@1b785d9 Implement Snapshot & Restore modules Create snapshots #19
• CodeChain-io/codechain@403b519 Fetch snapshot header from peers Import the snapshot header #29
• CodeChain-io/codechain@f4af598 Make the snapshot header importable without parent Import the snapshot header #29
• CodeChain-io/codechain@be35914 Update snapshot message format Update messages of the block sync extension #28
• CodeChain-io/codechain@a8627c2 Import only desired bootstrap headers Import the snapshot header #29
• CodeChain-io/codechain@ecdaa3a Implement snapshot service Create snapshots #19
• CodeChain-io/codechain@27e3c4e Add RPC devel_snapshot Add RPCs for managing snapshots #20
• CodeChain-io/codechain@ef1a176 Add basic e2e test for snapshot Add RPCs for managing snapshots #20
• CodeChain-io/codechain@b3cc277 Rename total_score to nonce in sync message Update messages of the block sync extension #28
• CodeChain-io/codechain@443a178 Add SnapshotNotifySender to Tendermint worker Create snapshots #19
• CodeChain-io/codechain@4e5ba6b Implement snapshot on term end Create snapshots #19
• CodeChain-io/codechain@7490d25 Add snapshot sync test with Tendermint dynamic validator
• CodeChain-io/codechain@6d5af4d Send and receive snapshot chunk requests
• CodeChain-io/codechain@fe9c785 Serve snapshot responses to peers
• CodeChain-io/codechain@ef3ad4f Use binding for match clause
• CodeChain-io/codechain@cbe8322 Add RPC snapshot_getList Add RPCs for managing snapshots #20
• CodeChain-io/codechain@af90610 Add autoremoving expired snapshot feature Create snapshots #19
• CodeChain-io/codechain@a96282d Detect bootstrap header in tendermint worker Import the snapshot header #29
• CodeChain-io/codechain@cc236fd Add sync state SnapshotBody
• CodeChain-io/codechain@0ba5323 Move to SnapshotBody state after downloading the snapthot header
• CodeChain-io/codechain@abe60a3 Import snapshot block with body
• CodeChain-io/codechain@9354d8d Update the best block after importing snapshot chunks
• CodeChain-io/codechain@eb6b204 Refactor block::Extension::transtition_to_full()
• CodeChain-io/codechain@afcf587 Change sync extension to update pivot after transitioning to Full
• CodeChain-io/codechain@0c598ce Fix to receive peer requests from just connected nodes
• CodeChain-io/codechain@2877685 Defer sending peer status after transitioning to full sync mode
• CodeChain-io/codechain@d8368c5 Factor out snapshot notify Create snapshots #19
• CodeChain-io/codechain@9ce70ad Move send_snapshot_notify() before the early return Create snapshots #19
• CodeChain-io/codechain@ed78493 Defer snapshot timing by one block in Tendermint Create snapshots #19
• CodeChain-io/codechain@d925fec Fix snapshot block estimation in test
• CodeChain-io/codechain@18f8fa7 Introduce CurrentValidators Update tendermint implementation to be compatible with snapshot sync #27
• CodeChain-io/codechain@275a671 Get tendermint validators with CurrentValidators Update tendermint implementation to be compatible with snapshot sync #27
• CodeChain-io/codechain@f192340 Generate snapshot chunks for shard level state Create snapshots #19
• CodeChain-io/codechain@8a428cb Refactor on_chunk_response
• CodeChain-io/codechain@f628350 Refactor sync state transition
• CodeChain-io/codechain@364fa18 Import shard trie chunks in sync extension