The testing interface does not take nixpkgs as a parameter anymore => fix this
Fix run-in-machine testcase + add it to the tests
Unify the two Memtest modules

This means we now have Memtest86+ on the installation CD.
Move run-in-machine test to a different place, because it does not conform to the other testcases' interface
Use "cp" instead of "rsync" for VirtualBox image generation

Rsync appears to use a lot of memory.  Fixes #266.
try to fix zfs into initrd