Added autoloader to plugin loader, executor improvements

plugins/executor/Helper.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace VfxApply\Plugin\Executor;
+
+use VfxApply\Plugin;
+use VfxApply\Input;
+use VfxApply\Output;
+use VfxApply\Preset;
+
+class Helper
+{
+    protected $body;
+
+    protected $script;
+
+    public function __construct($body)
+    {
+        $this->body = $body;
+    }
+
+    public function setScript(Script $script)
+    {
+        $this->script = $script;
+    }
+
+    public function call(array $env)
+    {
+        $body = "<?php ".preg_replace_callback('/(\{\{\%([a-z]+)\}\})/', function ($m) use ($env) {
+            return $env[$m[2]];
+        }, $this->body);
+
+        $tmpname = tempnam(null, "vfxhelper");
+        file_put_contents($tmpname, $body);
+        passthru("php {$tmpname}");
+        unlink($tmpname);
+    }
+}
+