Improve high-level benchmarks, sending coins with fees at abci level

[ethanfrey]

Followup story #284

[husio]

Initial work is in https://github.com/iov-one/weave/tree/benchmarks_on_real_bnsd branch. It appears to be harder to write than initially expected.
For now, waiting for the development of #375 I think that having a bnsd client would make this task much easier.

[ethanfrey]

Please take the time to refactor the abci level benchmarks well. Especially to consider the api you want. I think we made huge progress on adding clarity this morning.

Writing over tendermint is harder than directly on the app, but we would like to expose a similar interface. And would need to add more features as well.

Once we get clarity on apis from this refactoring, we will be much clearer on what we want from a client

[ethanfrey]

🎉

[husio]

Slowly getting "there" with the tests 😉