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/Rest/ApiContextTest.php

@@ -3,7 +3,7 @@
 use PayPal\Rest\ApiContext;
 
 /**
- * Test class for PPAPIService.
+ * Test class for ApiContextTest.
  *
  */
 class ApiContextTest extends PHPUnit_Framework_TestCase