Create %clockstep agent

[tiller-tolbus]

Within our new proof of concept %lockstep agent that implements a simple spec for the Tendermint protocol. One of the main error cases we have found in our testing is difficulty in getting the step timer to fire reliably within a mono-agent. A new agent %clockstep should abstract away the timer and expose the routine calls to process steps in the protocol as a subscription to %lockstep.

[tiller-tolbus]

Finished by @polwex