Added an ability to provide Curl Options in Configuration

- Removed http.Retry, and http.ConnectionTimeout from configuration
- Added ability to provide Constant and its value in Configuration File

lib/PayPal/Auth/OAuthTokenCredential.php

@@ -204,7 +204,7 @@ class OAuthTokenCredential extends PayPalResourceModel
      */
     private function getToken($config, $clientId, $clientSecret, $payload)
     {
-        $httpConfig = new PayPalHttpConfig(null, 'POST');
+        $httpConfig = new PayPalHttpConfig(null, 'POST', $config);
 
         $handlers = array(self::$AUTH_HANDLER);