Merge branch 'master' into dp/chore/fetch-dependencies-from-crates

* master:
  Contracts: Per block gas limit (#506)
  Make sure to ban invalid transactions. (#615) (#620)
  Forward-port BFT fixes from v0.2 and restructure agreement cancelling (#619)
  Allow specifying listening multiaddresses (#577)
  Introduce Runtime Events (#607)
  update substrate/extrinsic-pool (#616)
  add a new unit test for extrinsic pool (#611)
  set the current repo in Cargo.toml (#610)
  add cli for purge chain (#609)