Define django_loaded signal so we can properly connect our own.

Review Request #968 — Created Aug. 16, 2009 and submitted — Latest diff uploaded


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Email notification wasn't getting properly connected to the
publish signals because the file wasn't loaded. And
connecting them in breaks because django isn't
loaded yet.

With the django_loaded signal, we can delay connecting signals
until we're sure all we need is there.
All tests pass.