Make the app single process only, including the following fixes:

1) Simplify SharedPreferences management
2) Shut down signalManager/splitManager to avoid random crashes
3) Get rid of sharedPreferencesChanged from the service interface

All tests pass.

MyTracks/src/com/google/android/apps/mytracks/services/TaskExecuterManager.java

@@ -15,10 +15,10 @@
  */
 package com.google.android.apps.mytracks.services;
 
-import android.util.Log;
-
 import com.google.android.apps.mytracks.MyTracksConstants;
 
+import android.util.Log;
+
 /**
  * This class will manage a period task executer.
  *
@@ -26,13 +26,12 @@ import com.google.android.apps.mytracks.MyTracksConstants;
  */
 public class TaskExecuterManager {
 
-  int frequency;
-  PeriodicTask task;
-  PeriodicTaskExecuter executer;
+  private int frequency;
+  private PeriodicTask task;
+  private PeriodicTaskExecuter executer;
 
-  public TaskExecuterManager(int frequency,
-                             PeriodicTask task,
-                             TrackRecordingService service) {
+  public TaskExecuterManager(int frequency, PeriodicTask task,
+	  TrackRecordingService service) {
     this.task = task;
     setFrequency(frequency, service);
   }
@@ -69,7 +68,7 @@ public class TaskExecuterManager {
   }
 
   /**
-   * Restore the task at the current frequency.
+   * Restores the task at the current frequency.
    */
   public void restore() {
     if (frequency > 0) {
@@ -77,4 +76,13 @@ public class TaskExecuterManager {
       executer.scheduleTask(frequency * 60000);
     }
   }
+  
+  /**
+   * Shuts down this executer.
+   */
+  public void shutdown() {
+    if (executer != null) {
+      executer.shutdown();
+    }
+  }
 }