Removing Dependency from SDK Core Project

- Copied files required for Rest API SDK
- Removed PPApiContext and directly connected APIContext with PPConfigManager
- Removed duplicate data storage of configuration and credentials.
- Code Style Fixes
- Remove build.xml file as it is not required anymore
- Updated the samples
- Updated the documentations

lib/PayPal/Api/RelatedResources.php

@@ -117,9 +117,9 @@ class RelatedResources extends PPModel
 
     /**
      * Set Order
-     * 
+     *
      * @param \PayPal\Api\Order $order
-     * 
+     *
      * @return $this
      */
     public function setOrder($order)
@@ -131,7 +131,7 @@ class RelatedResources extends PPModel
 
     /**
      * Get Order
-     * 
+     *
      * @return \PayPal\Api\Order
      */
     public function getOrder()