Move PHUIFormBoxView to PHUIObjectBoxView

Summary: I'd like to reuse this for other content areas, renaming for now. This might be weird to keep setForm, but I can fix that later if we need.

Test Plan: reload a few forms in maniphest, projects, differential

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: Korvin, aran

Differential Revision: https://secure.phabricator.com/D7120

src/applications/differential/controller/DifferentialDiffCreateController.php

@@ -82,7 +82,7 @@ final class DifferentialDiffCreateController extends DifferentialController {
           ->addCancelButton($cancel_uri)
           ->setValue(pht("Create Diff")));
 
-    $form_box = id(new PHUIFormBoxView())
+    $form_box = id(new PHUIObjectBoxView())
       ->setHeaderText(pht('Create New Diff'))
       ->setFormError($errors)
       ->setForm($form);