Fix an issue with creating tasks directly into workboard columns

Summary:
See <https://discourse.phabricator-community.org/t/tasks-created-via-workboard-column-menu-are-moved-to-wrong-column/2200>. The recent `setIsConduitOnly()` / `setIsFormField()` change (in D19842) disrupted creating tasks directly into a column from the workboard UI.

This field //is// a form field, it just doesn't render a visible control.

Test Plan:
  - Created a task directly into a workboard column. Before: column selection ignored. After: appeared in correct column.
  - Used "move on workboard" comment action.
  - Edited tasks; edited forms for tasks. Didn't observe any collateral damage (weird "Column" fields being present).

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D19870

src/applications/maniphest/editor/ManiphestEditEngine.php

@@ -169,7 +169,9 @@ EODOCS
         ->setConduitDocumentation($column_documentation)
         ->setAliases(array('columnPHID', 'columns', 'columnPHIDs'))
         ->setTransactionType(PhabricatorTransactions::TYPE_COLUMNS)
-        ->setIsFormField(false)
+        ->setIsReorderable(false)
+        ->setIsDefaultable(false)
+        ->setIsLockable(false)
         ->setCommentActionLabel(pht('Move on Workboard'))
         ->setCommentActionOrder(2000)
         ->setColumnMap($column_map),