View source for Update:Remora Database Replication

* Method
** Cake determines which db to use by the $useDbConfig var in the Model, so in order to implement rw/ro we need to change that var to the correct database. We default to the read-only Shadow db, and change to the default db only when performing a write operation, ideally, though some models may need to read from the rw db because they can't tolerate any replication lag.
** This is pretty simple for the Save and Del methods.