Implement delivery receipts.

1) Support a "receipt" push message type.

2) Identify messages by timestamp.

3) Introduce a JobManager to handle the queue for network
   dependent jobs.

src/org/thoughtcrime/securesms/ApplicationContext.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2013 Open Whisper Systems
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.thoughtcrime.securesms;
+
+import android.app.Application;
+import android.content.Context;
+
+import com.path.android.jobqueue.JobManager;
+import com.path.android.jobqueue.config.Configuration;
+
+import org.thoughtcrime.securesms.crypto.PRNGFixes;
+import org.thoughtcrime.securesms.jobs.ContextInjector;
+import org.thoughtcrime.securesms.jobs.GcmRefreshJob;
+import org.thoughtcrime.securesms.jobs.JobLogger;
+import org.thoughtcrime.securesms.util.TextSecurePreferences;
+
+/**
+ * Will be called once when the TextSecure process is created.
+ *
+ * We're using this as an insertion point to patch up the Android PRNG disaster,
+ * to initialize the job manager, and to check for GCM registration freshness.
+ *
+ * @author Moxie Marlinspike
+ */
+public class ApplicationContext extends Application {
+
+  private JobManager jobManager;
+
+  public static ApplicationContext getInstance(Context context) {
+    return (ApplicationContext)context.getApplicationContext();
+  }
+
+  @Override
+  public void onCreate() {
+    initializeRandomNumberFix();
+    initializeJobManager();
+    initializeGcmCheck();
+  }
+
+  public JobManager getJobManager() {
+    return jobManager;
+  }
+
+  private void initializeRandomNumberFix() {
+    PRNGFixes.apply();
+  }
+
+  private void initializeJobManager() {
+    Configuration configuration = new Configuration.Builder(this)
+        .minConsumerCount(1)
+        .injector(new ContextInjector(this))
+        .customLogger(new JobLogger())
+        .build();
+
+    this.jobManager = new JobManager(this, configuration);
+  }
+
+  private void initializeGcmCheck() {
+    if (TextSecurePreferences.isPushRegistered(this) &&
+        TextSecurePreferences.getGcmRegistrationId(this) == null)
+    {
+      this.jobManager.addJob(new GcmRefreshJob());
+    }
+  }
+
+}