Added raw_body to posts.byThread

Added the post.raw_body property to list of posts returned by the
posts.byThread call. This should allow the editor to show the editing
user the original text they last put in.
Thread sorted by updated_at, post.create updates thread updated_at

Added more code to the posts.create method that updates the thread's
updated_at property if the new post has a later timestamp. Also, the
threads.byBoard query has also been changed to order threads by
updated_at rather than by thread ids.

To make that last query faster, the thread table has a new index on
updated_at.