Added ESSENTIALS_VERSION to the save file (with backwards compatibility)

Data/Scripts/016_UI/014_PScreen_Save.rb

@@ -24,6 +24,7 @@ def pbSave(safesave=false)
        Marshal.dump($PokemonMap,f)
        Marshal.dump($PokemonBag,f)
        Marshal.dump($PokemonStorage,f)
+       Marshal.dump(ESSENTIALS_VERSION,f)
     }
     Graphics.frame_reset
   rescue
@@ -153,4 +154,4 @@ def pbSaveScreen
   screen = PokemonSaveScreen.new(scene)
   ret = screen.pbSaveScreen
   return ret
-end
+end