Release Candidate 0.13.0

Breaking changes

• Ported exonum-btc-anchoring to a new version of Exonum with support
  of dynamic services. (#145)

  In this way, a large number of changes have occurred in service business logic:

  • Nodes performing anchoring are no longer strictly associated with the
    validator nodes. It means that there may exist a validator node that does not
    perform anchoring, and vice versa an anchoring node that is not a validator.
    But we strongly recommend to keep one to one relationship between the
    anchoring and validator nodes.
  • The bootstrapping procedure has been completely changed in accordance with
    the fact that the service can be started at any time during the blockchain
    life. The implementation of the service has become stateless and all logic
    that previously was performed in the after_commit method was taken out
    in a separate btc_anchoring_sync utility.
  • "v1" prefix has been removed from API endpoints and introduced a lot of
    private API endpoints for the btc_anchoring_sync util.
  • Removed cryptographic proofs for Exonum blocks feature.
    It will be implemented as separate service.
  • Funding transaction entry in config has been replaced by the add-funds
    endpoint in the anchoring private API. This means that you no longer need
    to use the configuration update procedure in order to add a new funding
    transaction. Now there is a simpler voting procedure with the help of the
    add-funds endpoint. A qualified majority of nodes (2/3n+1) just have
    to send the same transaction so that it is used as a funding one.

Internal improvements

• exonum_bitcoinrpc crate has been replaced in favor of bitcoincore-rpc. (#145)