expose client destroy (#979)

* expose client destroy

* fixed duplicate method

Author: mtrezza

parse/src/main/java/com/parse/Parse.java

@@ -191,7 +191,12 @@ public Void then(Task<Void> task) {
         }
     }
 
-    static void destroy() {
+    /**
+     * Destroys this client and erases its local data store.
+     * Calling this after {@code Parse.initialize} allows you to re-initialize this client
+     * with a new configuration.
+     */
+    public static void destroy() {
         ParseObject.unregisterParseSubclasses();
 
         ParseEventuallyQueue queue;