Follow-up from this commit - 9b8af0ea9f
Adds helpful data into MovedPost records for later lookup. ALSO fixes notifications for freeze_original to point to the newly created post, not the moved post.
This is a very simple change, which creates a permanent table in the DB, rather than generating a temporary table when moving posts. This change is about capturing data and any usage will appear in a follow-up.
I did include a new column created_new_topic in the new table, so that it can be easily audited without having to compare destination topic created_at with moved_post records.
