make xyweb act as upgrader

```
Hello,
as a idea:
try to make xyweb also perform upgrades from one version to the other.

So a user would start xy home and have a button "check for upgrades".
If a new upgrade is available, these could be downloaded and installed in
background.

What do you think?
```

Original issue reported on code.google.com by `tim.mich...@gmail.com` on 6 Jan 2009 at 11:17
