Moved models to DbModels, instead of using [Persistent] attribute.
Revamped NHibernate configuration.

Fixed some mistakes. Added mapping for the Noda Time's Instant type
(other types won't be needed in persistence layer right now). Moved
things around. Added logging integration (yes, that is another logger
factory and wrapper, I don't really care tbh; we can look into that
later).
Added migrations skeleton. Not functional yet.