ref #966

This issue is part of implementing the generate, sign, send workflow for offline transaction generation. It should also be a place to discuss implementation details for gaiacli broadcast

Description

As a gaiacli user
I want to execute a Tx that was generated and signed beforehand
So that I can validate and broadcast the transaction.

Acceptance Criteria

Given a signed transaction
When I run gaiacli broadcast
Then the transaction is validated and broadcasted.