Post status/searching on a Blog.

This is meant to pull answers to the questions "what's the visibility of this Post entity to this User entity" and "what do we tell this User entity that this Post entity's publication date/status is" out of the Post entity proper in an attempt to simplify that entity and its CCO (which no longer has to care about this). The CCO will never be called (and thus the entity will never be instantiated) in response to a controller action for a user other than the author of a draft post. For a public post, this *should* make it easier to find the authoritative source for the formatted publication date (once the redundancy is stripped out).