Do more to keep MessageRetrievalService alive

Closes #6456

AndroidManifest.xml

@@ -514,6 +514,13 @@
         </intent-filter>
     </receiver>
 
+    <receiver android:name=".service.BootReceiver">
+        <intent-filter>
+            <action android:name="android.intent.action.BOOT_COMPLETED"/>
+            <action android:name="org.thoughtcrime.securesms.RESTART"/>
+        </intent-filter>
+    </receiver>
+
     <receiver android:name=".service.DirectoryRefreshListener">
         <intent-filter>
             <action android:name="android.intent.action.BOOT_COMPLETED" />

src/org/thoughtcrime/securesms/service/BootReceiver.java

@@ -0,0 +1,15 @@
+package org.thoughtcrime.securesms.service;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+
+public class BootReceiver extends BroadcastReceiver {
+
+  @Override
+  public void onReceive(Context context, Intent intent) {
+    Intent messageRetrievalService = new Intent(context, MessageRetrievalService.class);
+    context.startService(messageRetrievalService);
+  }
+
+}

src/org/thoughtcrime/securesms/service/MessageRetrievalService.java

@@ -87,6 +87,8 @@ public class MessageRetrievalService extends Service implements InjectableType,
     if (retrievalThread != null) {
       retrievalThread.stopThread();
     }
+
+    sendBroadcast(new Intent("org.thoughtcrime.securesms.RESTART"));
   }
 
   @Override
@@ -236,7 +238,7 @@ public class MessageRetrievalService extends Service implements InjectableType,
       Log.w(TAG, "Exiting...");
     }
 
-    public void stopThread() {
+    private void stopThread() {
       stopThread.set(true);
     }