Add a reminder that with great power comes great responsibility
Add an abstraction for modifying state when dumping

And use it so that we continue to populate the old
:reloading_for_preload_upgrade field for downgrades.

(This is mostly useful for downgrade compatibility)
Handle upgrades from version before the :reloading_for_upgrade rename
Add a log message if we have to upgrade config
Look at the right hash when finding added/missing keys
Add an explanatory comment
Add a TODO to cleanup the backwards compatibility code