Implement Cheap Heterogeneous Paxos Blockchain Creation

[isheff]

When our nodes can run multiple chains, and we have a spec of Heterogeneous Paxos modified for blockchains, we want the ability to "spin-up" new Heterogeneous Paxos quickly an easily.

• clients should be able to request starting a new chain easily
• these chains should add new blocks only as necessary, and use few resources when they have no transactions to commit