Suggest elevation if saving fails with Access Denied

If File > Elevate (#166) is unchecked then change OK alert box to Yes/No (keeping the alert icon), with this line of text added:

```
[Error saving ...]
[Access is denied.]
Elevate and try again?
```

Upon Yes, trigger File > Elevate, then if succeeded (user didn't cancel, correct authorization, etc.) trigger File > Save.