Renaming Namespaces and Organizing Classes

- Updated OpenId classes to be in API namespace
- Updated PP Naming Convention to PayPal Naming Convention
- FormatConverter Class got its own namespace
- Handlers are grouped in Handler namespace
- Samples and Tests Updated Accordingly

tests/PayPal/Test/Common/NestedClass.php

@@ -1,9 +1,9 @@
 <?php
 namespace PayPal\Test\Common;
 
-use PayPal\Common\PPModel;
+use PayPal\Common\PayPalModel;
 
-class NestedClass extends PPModel
+class NestedClass extends PayPalModel
 {
 
     public function setId($id)
@@ -33,4 +33,4 @@ class NestedClass extends PPModel
     {
         return $this->info;
     }
-}
+}