Grey out save/load buttons if it's disabled in script.

```
If an author has decided to disable saving or loading in one of the scripts, 
then the menu should have the buttons greyed out, instead of having the player 
click on them and then go back to the game. This should be a visible clue to 
the player that "No, you cannot save here."
```

Original issue reported on code.google.com by `earlAcda...@gmail.com` on 23 Mar 2014 at 7:45
