This commit addes a combined blog feed that shows all posts of all
subscribed blogs in the order the blog posts have been received.
For now, this commit also hides other blog functionality like adding
additional blogs and browsing individual blogs.
Closes#417
Removes teaser and makes body mandatory.
It also adds support for deleting blogs and
introduces a getAuthorStatus() method to the IdentityManager
that takes a running transaction.
This implements a simple initial blog client that covers the basic blog
actions, but no deletion/removal of blogs, yet.
Classes for Blogs and Blog Post Headers have been introduced along with
the associated factories.
A `BlogPostValidator` has been added that validates incoming blog posts.
Closes#402Closes#404
