Fix the confirmation workflow, which was broken in several places.

[leonardr]

This branch fixes a number of problems with the email confirmation workflow, all of them located in untested routing code.

• The confirm_resource function took the wrong arguments.
• It referred to a LibraryRegistry.validation_controller object, but that object was not instantiated during startup.
• It called the method ValidationController.validate when the actual name of the method is confirm.

I've done an end-to-end test locally to make sure there are no more problems with this process.