Exonum 0.8 "Great Grey Owl"

Breaking changes

• The anchoring service has been switched to using p2wsh address format. (#123)
  It now uses segwit addresses....
  This change increases the limit on the number of validators and anchoring security
  as well as reduces fees for applying thereof.

  Note that the old format of anchoring transactions is incompatible with the new one.
  Hence, update of the existing blockchain to the new anchoring version is not possible.
  For use of a new anchoring format a new blockchain has to be launched.

New features

• Introduced a new API method /v1/block_header_proof/:height that provides cryptographic
  proofs for Exonum blocks including those anchored to Bitcoin blockchain.
  The proof is an apparent evidence of availability of a certain Exonum block
  in the blockchain. (#124)

Internal improvements

• Updated to the Rust-bitcoin 0.13
  release (#123).

Fixed

• Fixed bug with the nearest_lect endpoint that sometimes didn't return actual data [ECR-1387]. (#125)