CONN-512 checkpointing commit for potential fix

Adding a ArticleDeleteComplete hook in ForumHookHelper to
update the comments_index record if it exists.

This is a WIP. It's not working as expected in dev.
CONN-512 the comment deletion within trans block

The comment deletion needs to happen within the transaction block. OTW,
the page->comments_index association will not exist. Moved the
behavior to the ArticleDoDeleteArticleBeforeLogEntry hook.
CONN-512 cleanup comments
CONN-512 add maint script to fix comments_index

Adding a maintenance script to clean up the bad rows in the
comments_index table. Finds entries with first_rev_id values that have
no corresponding rows in the revision table and sets deleted=1.

/cc @owend
CONN-512 fixing whitespace
CONN-512 grr. more whitespace
CONN-512 formatting cleanup in ForumHooksHelper

I'm remapping my muscle memory to Wikia conventions.
CONN-512 move doDeleteUpdates after the hook

`doDeleteUpdates` has [side
effects](https://github.com/Wikia/app/blob/CONN-512/includes/WikiPage.php#L2129-2133)
that effectively reset the page. This disables hook logic that
needs to manipulate the page being deleted or it's associations. In this
case, we need update the comments index row that is associated with this
page and mark it as deleted.

This fix is brittle. IMHO there should be FK constraints from
`comments_index.first_rev_idi` -> `revision.rev_id` that cascade on
delete.
Merge pull request #3574 from Wikia/CONN-512

CONN-512 Fixing dangling comments_index records left from Special:Nuke