Bug 40030: Install HTTPS Everywhere and NoScript addons on startup

HTTP Everywhere is installed as a builtin extension and NoScript as
a regular AMO addon. To avoid unnecessary I/O we only install NoScript
the first time, and rely on the browser addon updating mechanism for
keeping up with new versions. This is the same behaviour that was
implemented in the Fennec-based Tor Browser, where it was installed
as a "distribution addon", which also only occurred once.
2 jobs for 40030 in 39 minutes and 50 seconds (queued for 2 seconds)