fix Bug 443371 - Refine documentation

Remove 'public' keyword from the classes which are not requried to be exposed to application.\
Add and refine comments to generate java doc.

bug 443371

Change-Id: Ic6c1cdf7674a113478f010ab79264e12478670d5
Signed-off-by: tzihan <zhtang@cn.ibm.com>

Author: tzihan

org.eclipse.paho.android.service/org.eclipse.paho.android.service/src/org/eclipse/paho/android/service/AlarmPingSender.java

@@ -37,7 +37,7 @@
  *
  * @see MqttPingSender
  */
-public class AlarmPingSender implements MqttPingSender {
+class AlarmPingSender implements MqttPingSender {
 	// Identifier for Intents, log messages, etc..
 	static final String TAG = "AlarmPingSender";
 

org.eclipse.paho.android.service/org.eclipse.paho.android.service/src/org/eclipse/paho/android/service/DatabaseMessageStore.java

@@ -27,7 +27,7 @@
  * Implementation of the {@link MessageStore} interface, using a SQLite database
  * 
  */
-public class DatabaseMessageStore implements MessageStore {
+class DatabaseMessageStore implements MessageStore {
 
 	// TAG used for indentify trace data etc.
 	private static String TAG = "DatabaseMessageStore";

org.eclipse.paho.android.service/org.eclipse.paho.android.service/src/org/eclipse/paho/android/service/MessageStore.java

@@ -31,7 +31,7 @@
  * used.
  * </ul>
  */
-public interface MessageStore {
+interface MessageStore {
 
 	/**
 	 * External representation of a stored message