Allow Maniphest tasks to be filtered by Project

Summary:
Major things taking place here:

  - A new table for storing <task, project> relationships.
  - Moved all task query logic into a dedicated class.
  - Added a "projects" filter to the UI.

I was originally going to try to drive this off the main search index but the
perf benefits of a custom schema make an overwhelming argument in favor of doing
it this way.

Test Plan:
Filtered tasks by author and owner and zero, one, and more than one project.
Exercised all the group/sort options. Ran the index script over my 100k task
corpus. Edited task-project membership and verified the index updated.

Reviewed By: cadamo
Reviewers: gc3, jungejason, cadamo, tuomaspelkonen, aran
CC: aran, cadamo, epriestley
Differential Revision: 556

scripts/search/reindex_maniphest.php

@@ -0,0 +1,32 @@
+#!/usr/bin/env php
+<?php
+
+/*
+ * Copyright 2011 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.
+ */
+
+$root = dirname(dirname(dirname(__FILE__)));
+require_once $root.'/scripts/__init_script__.php';
+require_once $root.'/scripts/__init_env__.php';
+
+ini_set('memory_limit', -1);
+$tasks = id(new ManiphestTask())->loadAll();
+echo "Updating relationships for ".count($tasks)." tasks";
+foreach ($tasks as $task) {
+  ManiphestTaskProject::updateTaskProjects($task);
+  echo '.';
+}
+echo "\nDone.\n";
+