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

sample/payment-experience/ListWebProfiles.php

@@ -10,7 +10,7 @@ $apiContext = require __DIR__ . '/../bootstrap.php';
 // (See bootstrap.php for more on `ApiContext`)
 try {
     $list = \PayPal\Api\WebProfile::get_list($apiContext);
-} catch (\PayPal\Exception\PPConnectionException $ex) {
+} catch (\PayPal\Exception\PayPalConnectionException $ex) {
     ResultPrinter::printError("Get List of All Web Profiles", "Web Profiles", null, null, $ex);
     exit(1);
 }