Plugin manager, misc fixes

* Fixed an error when trying to create nonexisting resource type
* Updated the init-command to create plugins and scipts directories
* Added a basic installer function

src/SparkApplication.php

@@ -39,6 +39,10 @@ class SparkApplication extends Application
         $this->add(new Commands\ReplCommand());
         $this->add(new Commands\InitCommand());
 
+        if (getenv("SPARK_PLUGINS")) {
+            $this->add(new Commands\PluginsCommand());
+        }
+
     }
 
     public function getPluginManager(): PluginManager