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

lib/PayPal/Core/PayPalLoggingLevel.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace PayPal\Core;
+
+/**
+ * Logging Levels.
+ * Class containing all the constants for Logging Levels.
+ */
+class PayPalLoggingLevel
+{
+
+    // FINE Logging Level
+    const FINE = 3;
+
+    // INFO Logging Level
+    const INFO = 2;
+
+    // WARN Logging Level
+    const WARN = 1;
+
+    // ERROR Logging Level
+    const ERROR = 0;
+}