added initial support for service definition

ServiceDefinition/Loader/FileLoader.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Bundle\WebServiceBundle\ServiceDefinition\Loader;
+
+abstract class FileLoader implements LoaderInterface
+{
+    protected $file;
+
+    public function __construct($file)
+    {
+        if (!file_exists($file)) {
+            throw new \InvalidArgumentException(sprintf('The service definition file %s does not exist', $file));
+        }
+
+        if (!is_readable($file)) {
+            throw new \InvalidArgumentException(sprintf('The service definition file %s is not readable', $file));
+        }
+
+        $this->file = $file;
+    }
+}