Enable VirtualBox guest additions by default (Closes: #5730)
Install TBB in a custom way instead of installing Iceweasel.

Instead of installing the iceweasel package (and friends) we now fetch
the TBB tarballs at build-time and extract the Tor Browser, browser
add-ons and langpacks, and browser user data into sensible places. We
try to keep something like the old organization as much as possible.

Unfortunately this drops language support to whatever subset that the
TBB supports.
Drop conflicting dpkg option.
Use long option name.
Rely on tar's automatic compression detection.
Remove spurious white-spaces.
Work around Tor Browser's hardcoded profile path when running Tor Launcher.
Don't pass -f to rm.

We `set -e` and definitely do no expect an error here.
Escape dots in regex.
Explicitly extract expected directory from archive.

If the name of the Tor Browser directory ever changes the script will
fail here with an informative error message.
Use `cp -a` to preserve more inode info.
Refer to relevant ticket.
Remove the iceweasel wrapper script.

It's unused now that we use the TBB.
Read Tails' documentation with the Tor Browser.

We don't have iceweasel any more.
Remove comment about ibus.

No need to copy the TBB start script's ibus stuff since it works just
fine as-is.
Fix getTorBrowserUserAgent script.

With TBB, the prefs we look for are hidden inside an archive.
Refresh translations.
Use apt-config instead of custom sed:ing.
Build fake package in TMP dir.

We don't want to leave traces in /root by mistake.
Also set permissions/ownership for TBB extensions dir.

At some point it may not be a sub-dir of the TBB install dir.