Introduced common exception superclass

CloudObjects/SDK/Common/CryptoHelper.php

@@ -6,7 +6,7 @@
 
 namespace CloudObjects\SDK\Common;
 
-use Exception;
+use CloudObjects\SDK\Exceptions\SDKException;
 use ML\IRI\IRI;
 use CloudObjects\SDK\NodeReader;
 use Defuse\Crypto\Key, Defuse\Crypto\Crypto;
@@ -55,7 +55,7 @@ class CryptoHelper {
      */
     public function __construct(ObjectRetriever $objectRetriever, ?IRI $namespaceCoid = null) {
         if (!class_exists('Defuse\Crypto\Crypto'))
-            throw new Exception("Run composer require defuse/php-encryption before using CryptoHelper.");
+            throw new SDKException("Run composer require defuse/php-encryption before using CryptoHelper.");
 
         $this->objectRetriever = $objectRetriever;
         $this->namespace = isset($namespaceCoid)