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

sample/payments/GetAuthorization.php

@@ -37,7 +37,7 @@ try {
 		Retrieved Authorization:
 		<?php echo $authorization->getId();?>
 	</div>
-	<pre><?php var_dump($authorization->toArray());?></pre>
+	<pre><?php echo $authorization->toJSON(JSON_PRETTY_PRINT);?></pre>
 	<a href='../index.html'>Back</a>
 </body>
 </html>