TBB Upstreaming of Yawning's Firejail Script

This ticket is to track the eventual inclusion for a Firejail aware start-tor-browser script in TBB releases - it attempts to run TBB in Firejail if detected on the system. Firejail is a popular and well maintained software containment system available in Debian.

(Yawning is very busy these days and won't be able to work on it. Thanks Yawning for writing it in the first place!)

Since a Tor Browser planned changes is to release versions that can take advantage of system containment features - this work complements it IMHO.

https://git.schwanenlied.me/yawning/tor-firejail

https://lists.torproject.org/pipermail/tor-dev/2016-May/010948.html