[Merge] livecd-rootfs:uc18-kassel into livecd-rootfs:ubuntu/master

[Chih-Hsyuan Ho]

Lukasz and Steve, we have decided to make all the necessary changes to the Kassel image to make it a proper and permanent solution as a subarch. Hugh, the project's lead engineer, will start the collaboration with your team to make that happen. Thanks.  
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https://code.launchpad.net/~ubuntu-core-dev/livecd-rootfs/+git/livecd-rootfs/+merge/366327
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