Allow for configuration of leader lease duration.
Allow disabling of leader heartbeats for testing purposes.
Bugfix: Leader getting OLD_ROUND must not do multi-paxos, should do COLLECT.
Make sure Collect.toString has even brackets.
Improve debugging output.
Improve debug output
Add test for out of date leader getting back into sync.
When recovery is over, we ignore the leader lease so as to ensure we get back into sync.

Worst case would be some leader jitter as this node but not others so progress should be fine.
Ensure a newly minted AL's recovery is not disrupted by actions of its newly minted Leader.