Query upgradeable tables on temporal schema :smirk:
Remove Rails initializer, to follow Rails' behaviour :grinning:

The initializer would trigger a database connection and check for
needed upgrades. Rails currently does not have this behavior, and
it connects to the database when an ActiveRecord is referenced.

This change makes ChronoModel do its stuff when it is actually
requested, following Rails' behavior.
Fix stupidity that lead to metadata loss :sweat:
Simplify comment fetch query :neckbeard: