Force close all activities before kill the app. Fixes #79.

src/com/xabber/android/data/ActivityManager.java

@@ -38,7 +38,7 @@ import com.xabber.androiddev.R;
  * @author alexander.ivanov
  * 
  */
-public class ActivityManager {
+public class ActivityManager implements OnUnloadListener {
 
 	private static final String EXTRA_TASK_INDEX = "com.xabber.android.data.ActivityManager.EXTRA_TASK_INDEX";
 
@@ -314,4 +314,9 @@ public class ActivityManager {
 		taskIndexes.put(activity, index);
 	}
 
+	@Override
+	public void onUnload() {
+		clearStack(true);
+	}
+
 }