Design doc needs to be updated wrt. the migration to Tor Browser

Grep’ing -i iceweasel should be a good start. I suspect a good number of pointers to files in our source code needs to be updated to, and something to be written about how we’re now installing the Tor Browser, splitting it in various places, things like this.

Feature Branch: feature/tor-browser-bundle

Parent Task: #7953 (closed)

Original created by @intrigeri on 7958 (Redmine)