Provide auto-increment option in attribute entry dialog

```
The dialog for entering polygon attributes defaults the values to the 
values that were previously entered. It would be good to provide an option 
to auto-increment (or decrement) the values for a selected numeric field 
(e.g lot number).
```

Original issue reported on code.google.com by `ola.stan...@gmail.com` on 24 Feb 2009 at 2:33
