mogdbsetup should print ALTER's with a dry-run option

```
It should be easier to convince mogdbsetup to print its intended SQL out 
without running anything, so people can review or apply the changes manually.

It might already do this but it doesn't seem obvious to me.
```

Original issue reported on code.google.com by `dorma...@rydia.net` on 2 Aug 2012 at 9:18
