Correct string interpolation of notifications.
Added proper dependencies on belongs_to's.

In most cases, we just want to drop the object if its object which it
belongs to is destroyed. However, with presentation, if the area is
suddenly removed, we don't want to drop the entire presentation and all
associated data.
Added validations for PasswordRecovery.
Removed usage of validates_associated.

It does not do what one thought it would.
Added validations for Notification.