Settings not preloaded in production
With the new update of Settings code, the possible options are not loaded in production at first run.
Fixes #2454 - Fix loading settings in production
The Setting subclasses are not preloaded in initialization phase in
Also (if Setting.first rescue (false)) is not satisfied when the
settings are not set yet. Using table_exists? instead.
Also, define constants before audited So that the constants are available even
when not migrated yet.