Move files in Phabricator one level up

Summary:
- `kill_init.php` said "Moving 1000 files" - I hope that this is not some limit in `FileFinder`.
- [src/infrastructure/celerity] `git mv utils.php map.php; git mv api/utils.php api.php`
- Comment `phutil_libraries` in `.arcconfig` and run `arc liberate`.

NOTE: `arc diff` timed out so I'm pushing it without review.

Test Plan:
/D1234
Browsed around, especially in `applications/repository/worker/commitchangeparser` and `applications/` in general.

Auditors: epriestley

Maniphest Tasks: T1103

src/aphront/response/AphrontFileResponse.php

@@ -0,0 +1,78 @@
+<?php
+
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @group aphront
+ */
+final class AphrontFileResponse extends AphrontResponse {
+
+  private $content;
+  private $mimeType;
+  private $download;
+
+  public function setDownload($download) {
+    $download = preg_replace('/[^A-Za-z0-9_.-]/', '_', $download);
+    if (!strlen($download)) {
+      $download = 'untitled_document.txt';
+    }
+    $this->download = $download;
+    return $this;
+  }
+
+  public function getDownload() {
+    return $this->download;
+  }
+
+  public function setMimeType($mime_type) {
+    $this->mimeType = $mime_type;
+    return $this;
+  }
+
+  public function getMimeType() {
+    return $this->mimeType;
+  }
+
+  public function setContent($content) {
+    $this->content = $content;
+    return $this;
+  }
+
+  public function buildResponseString() {
+    return $this->content;
+  }
+
+  public function getHeaders() {
+    $headers = array(
+      array('Content-Type', $this->getMimeType()),
+    );
+
+    if (strlen($this->getDownload())) {
+      $headers[] = array('X-Download-Options', 'noopen');
+
+      $filename = $this->getDownload();
+      $headers[] = array(
+        'Content-Disposition',
+        'attachment; filename='.$filename,
+      );
+    }
+
+    $headers = array_merge(parent::getHeaders(), $headers);
+    return $headers;
+  }
+
+}