Clean up more PonderAnswer cruft

Summary: Ref T2715. Ref T3578. Moves PonderAnswerQuery toward being policy-aware so we can use application PHIDs.

Test Plan: Viewed various Ponder things, voted on answers.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2715, T3578

Differential Revision: https://secure.phabricator.com/D6581

src/applications/ponder/controller/PonderVoteSaveController.php

@@ -25,7 +25,7 @@ final class PonderVoteSaveController extends PonderController {
     } else if ($this->kind == "answer") {
       $target = id(new PonderAnswerQuery())
         ->setViewer($user)
-        ->withPHID($phid)
+        ->withPHIDs(array($phid))
         ->executeOne();
     }