Update to Tor Browser 4.0

Current nightly builds live on https://people.torproject.org/~linus/builds/, which are built using https://gitweb.torproject.org/builders/tor-browser-bundle.git/blob/HEAD:/gitian/versions.nightly, which points currently to the tor-browser-31.1.1esr-4.x-1 branch where all the fixes for ESR 31 go to. Instead of GeKo’s one-shot build from October 1st, we should use the latest nightly build from there.

Feature Branch: feature/tor-browser-4.0

Original created by @intrigeri on 8026 (Redmine)

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