tor-browser-bundle: init at 7.0.1 (from source)

The original browser bundle expects to run from a bundled directory,
typically under user's home.  This version creates a firefox distribution
with preloaded extensions and settings that functions more like an
ordinary firefox installation.

The approach used here could be generalized to allow specification of
custom firefox distributions.  Eventually, the code will be factored so
that the tbb is just an instance of that more general construct (firefox
base + extensions + prefs).

Currently, we use the latest upstream versions of extensions and so on.
Eventually we want to track the upstream bundle more closely and ideally
use the exact same inputs (firefox source, extension sources).

To avoid mixing up profile data, all runtime state is stored under
$XDG_DATA_HOME/tor-browser.

Major TODO items
- Pluggable transports
- Upstream TBB version parity
- Avoid fetchgit
- Build NoScript from source (no upstream source repo, however, must rely
  on third-parties)
- Improved notation for packaging extensions
- Feature parity with the binary bundle (apulse and runtime purity, in
  particular)