[#6963] Disable import activities; create post-import activity

Signed-off-by: Tim Van Steenburgh <tvansteenburgh@gmail.com>
[#7047] quieter debugging when no request
[#7065] remove unindexed query to find slug in a different thread
[#7065] remove dead code for promoting post to its own thread

We haven't exposed this code to promote a post into its own thread
for a long time.  And it called ForumPost.move() which did an unindexed
query by slug, which is the reason to clean it up now.