Permissions for the Tor data directory are too permissive for control
sockets. We adapt them (and those for creating files) to the ones used
for Linux bundles by default. This fixes: #20076 and #20075 as FileUtils
is not needed anymore (and hence can't be missing in tl-utils.jsm).

On non-Windows platforms, use a Unix domain socket by default for the
Tor control port. New preferences:
  extensions.torlauncher.control_port_use_socket (Boolean)
  extensions.torlauncher.control_socket_path (path string)
New environment variable: TOR_CONTROL_SOCKET

When starting tor, always include a ControlPort argument so that
users can use environment variables to switch between the two control
port types.

Add a public TorGetControlSocketFile() function that Torbutton will
use to retrieve the socket file (an nsIFile) when a Unix domain
socket is in use.

Moved the getTorFile() function to our utilities module.

For Thunderbird/Instantbird, the CurProcD (topDir) is not browser/,
so we need to iterate one level less than Firefox.

These applications now use the same directory structure as Tor Browser.

Display a better error message if tor exits and Tor Launcher was
never able to establish a connection to the control port (pointing
users to a possible error in their torrc may help them find and
fix the startup problem themselves).