New boot images

[Gilad Bracha]

Just an FYI:

I've updated the boot images on the web site. There are enough changes since the last version that updating from the repos is tricky.

These images still work with the old VMs on the site. When we finally get reliable signed VMs from open Smalltalk, I'll update those as well, but so far, each new version has had some problem that makes it a worse option than the old ones.