Multi-State Machine Execution on Heterogeneous Paxos Chain

[isheff]

On a Heterogeneous Paxos chain, run a state machine for each "main chain," such that blocks can contain bundles of transactions on multiple chains. Note that:

• Not all nodes can / should execute all transactions
• We will ultimately need some kind of language for communicating these "bundles"
• We want to make as few assumptions as possible about the state machines from each "main chain."