[Merge] livecd-rootfs:origin/drop-lupin-casper into livecd-rootfs:ubuntu/master

[Michael Hudson-Doyle]

Review: Needs Fixing

We don't need to install lupin-casper any more but we do need to install casper -- I don't think it is getting pulled in any other way! IOW, this is more of a s/lupin-casper/casper/ job than outright code removal.
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https://code.launchpad.net/~ubuntu-core-dev/livecd-rootfs/+git/livecd-rootfs/+merge/415346
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