Added exceptions with base numbering 300

src/Database/Exception.php

@@ -0,0 +1,11 @@
+<?php
+namespace ProVM\Database;
+
+class Exception extends \Exception
+{
+    public function __construct(string $message = "", int $code = 0, ?Throwable $previous = null)
+    {
+        $code += 300;
+        parent::__construct($message, $code, $previous);
+    }
+}