Change Blog Paradigm to Short-Form

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.

briar-api/src/org/briarproject/api/blogs/BlogPostFactory.java

@@ -12,8 +12,8 @@ import java.security.GeneralSecurityException;
 public interface BlogPostFactory {
 
 	BlogPost createBlogPost(@NotNull GroupId groupId, @Nullable String title,
-			@NotNull String teaser, long timestamp, @Nullable MessageId parent,
+			long timestamp, @Nullable MessageId parent,
 			@NotNull LocalAuthor author, @NotNull String contentType,
-			@Nullable byte[] body)
+			@NotNull byte[] body)
 			throws FormatException, GeneralSecurityException;
 }