Currently chroot properties containing any OS can be added to any host. Of
course, some won't work. It would be nice to type check that the
combination of inner and outer OS are compatable (ie, some linux on some
linux).

I have a partially done patch for that, but it failed at the last hurdle.
See commit message 0b0ea182ab3301ade8b87b1be1cdecc3464cd1da 

[[!tag users/joey]]
