[Merge] ~mwhudson/livecd-rootfs/+git/livecd-rootfs:direct-casper-artifacts into livecd-rootfs:ubuntu/master

[Michael Hudson-Doyle]

PS: the auto/build diff is easier to read with -b!
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https://code.launchpad.net/~mwhudson/livecd-rootfs/+git/livecd-rootfs/+merge/502530
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