message: Explicitly inherit createMutableStorage in Storage
diff: @@ -60,6 +60,8 @@ namespace iroha {
  virtual expected::Result<void, std::string> insertPeer(
  const shared_model::interface::Peer &peer) = 0;
  + using MutableFactory::createMutableStorage;
  +
  /**
  * Creates a mutable storage from the current state
  * @return Created Result with mutable storage or error string
  