Upgrade to Linux 3.14

Originally created by @intrigeri on #7150 (Redmine)

Linux 3.14 landed in Debian unstable a few days ago. Linux 3.13 will disappear from it soonish. Presumably, we want to ship 3.14 in Tails 1.1.

Feature Branch: feature/linux-3.14

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information