filetype-767587: Add filesystem module

Add a dead simple filesystem module that has only a stat function right
now.
Only mozilla/util/filesystem.js needs review, the other changes don't
affect mozilla-central.

Signed-off-by: Joe Walker <jwalker@mozilla.com>
refactor-864370: Remove motivate() naffness

Which also means we are returning a string rather than html.

Does not need review for mozilla-central.

Signed-off-by: Joe Walker <jwalker@mozilla.com>
filetype-767587: Add 'file' type

Builds on the filesystem.js module added. Demo commands and tests to
follow.

Signed-off-by: Joe Walker <jwalker@mozilla.com>
filetype-767587: 'file' type unit tests and demos

Signed-off-by: Joe Walker <jwalker@mozilla.com>
refactor-864370: Fix Settings.getSetting bug

In GCLI settings names are short simple things, bug prefs in Firefox are
generally longer, so there is a prefix that we use when a GCLI setting
is stored in a Firefox pref. getSetting was failing to use this prefix.

Signed-off-by: Joe Walker <jwalker@mozilla.com>