Add tx log in websocket result.

[kraikov]

• I'm submitting a ...

  • bug report
  • feature request
  • support request => Please do not submit support request here, see note at the top of this template.

• What is the expected behavior?
  Provide the log of the transactions on WS events.

• What is the motivation / use case for changing the behavior?
  Currently, when someone wants to use the middleware to handle the contract events, when you receive the message, you need to call the rest api to get the tx log so you can decode the event. This whole step adds additional complexity to the dapp and additional dependency to the rest api.