[Tails-dev] [review'n'merge:1.1] feature/vagrant-wheezy-base…

Hi,

This branch makes it possible to build Tails from disk again, and as a
bonus it should make any future upgrades of the basebox painless for
users (and us thanks to the new documentation).

jvoisin has tested the Tails build (not basebox build), and a `rake
build` was all that was needed, so IMHO only a code review is necessary,
which I've assigned to intrigeri.

Cheers!