Put unavailable powerups at the end of the list

This causes a BIT of visible shuffling, but is pretty nice for
a few lines of css

gorge.css

@@ -370,6 +370,10 @@ button {
   transform: translate(0, 10px);
 }
 
+.upgrade-button.upgrade-button-inactive {
+  order: 999999;
+}
+
 .upgrade-button-inactive > .upgrade-icon-holder {
   opacity: 0.6;
 }