move currency to config file; change units to their own group in settings

config/phpvms.php

@@ -21,6 +21,15 @@ return [
      */
     'skin' => env('APP_SKIN', 'default'),
 
+    /**
+     * The ISO "Currency Code" to use
+     * http://www.xe.com/iso4217.php
+     *
+     * Note, do not change this after you've set it, unless you don't
+     * care that the currencies aren't "exchanged" into the new format
+     */
+    'currency' => 'USD',
+
     /**
      * Your vaCentral API key
      */