Add enough parity for CASE statements in ORDERs so that raw SQL is no longer needed

[wbond]

Ticket #603 by @khamer:

Perhaps an ordered array of conditions?

This allows for order statements to no longer depend no the database for execution, which means build related methods could have a method signature that allows for conditions, orders, and limits. While there's some risk of these build methods leaking more schema into views/controllers, it'll hopefully mostly replace the more common and worse $record->buildRelatedRecords()->filter($conditions).