Import of files bigger than 10MB fails due to max attachment size

Importing of a .xar file bigger than 10MB fails due to the maximum attachment size.

1) It doesn't make sense that this limit is in effect with .xar imports. Most wiki backups are bigger than 10MB.
2) For a new XWiki installation without any content, it's not trivial to increase the default attachment size. There does not exist a link to change objects and classes. The class editor is there and works, but it can only be accessed by directly entering the URL, which one has to know first.

Thanks,
Tobias