Move Maniphest attached files section into textbox.

Summary: Add a button to the Remarkup area that explains how to attach an image and remove the separate upload field.

Test Plan: Check that the dialog pops up correctly and that dropping images onto the Remarkup area works.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin, AnhNhan

Maniphest Tasks: T879

Differential Revision: https://secure.phabricator.com/D6049

src/applications/files/controller/PhabricatorFileUploadDialogController.php

@@ -0,0 +1,20 @@
+<?php
+
+final class PhabricatorFileUploadDialogController
+  extends PhabricatorFileController {
+
+  public function processRequest() {
+    $request = $this->getRequest();
+    $user = $request->getUser();
+
+    $dialog = id(new AphrontDialogView())
+      ->setUser($user)
+      ->setTitle(pht('Upload Image'))
+      ->appendChild(pht(
+        'To add files, drag and drop them into the comment text area.'))
+      ->addCancelButton('/', pht('Close'));
+
+    return id(new AphrontDialogResponse())->setDialog($dialog);
+  }
+
+}