* Move ledger write to its own stage
- Also, rename write_stage to leader_vote_stage, as write functionality
is moved to a different stage
* Address review comments
* Fix leader rotation test failure
* address review comments
* Add hooks for executing the storage contract
* Add store_ledger stage
Similar to replicate_stage but no voting/banking stuff, just convert
blobs to entries and write the ledger out
* Add storage_addr to tests and add new NodeInfo constructor
to reduce duplication...