We need to whitelist `[System+Principal]` for functioning settings
frames of WebExtensions on the about:addons page. On higher security
slider levels this is broken otherwise.

To quote Giorgio Maone (see: #25000 comment:14):

"The Tor Browser enforces permissions cascading, and in the Add-ons
Options window the top frame is about:addons, whose principal's origin
is [System+Principal]. Since this origin is omitted from Tor Browser's
version of NoScript mandatory whitelist, the top site by default is
considered forbidden, cascading down script blocking to the
WebExtension's subframe."

Kathleen Brade authored Feb 15, 2018 and boklm committed Feb 16, 2018

Tor Launcher's Moat client implementation uses Mozilla's Subprocess.jsm
module to start the meek client, and that module requires a complete
file path including the .exe suffix. For consistency, we now include
the .exe suffix everywhere.

Add a tbb_version.json file containing informations about the installed
bundle.

Patch provided by kkuehl, thanks

Use tor-browser -2 and build number bump

Changelog update and versions bump

The defaut timestamp value will use the commit time of the selected
commit for the project, which will require cloning the git repository if
it is not present. When we use the no_build_id target to display a script,
we usually don't care about such details, so we set timestamp to 0 to
avoid unnecessary cloning.

Versions bump and Changelog update