Create a decorator "ssl_fall_back" which catches a KamakiSSLError,
patches kamaki with the default certificates bundle and reruns the
failed method.

The decorator is used on the "SyncerSettings._get_pithos_client"
method, because this is the first point of SSL failure.

The default certificates bundle is acquired from the package
"certifi", which has been added to dependencies.

Before this patch, settings would be permanently saved only if
the state at the end of the modification was enough for a sync
to start.

After this patch, users will be able to save partial settings,
even if there are essential omissions.

Used to open the parent (containing) folder

In protocol.py, correct the WebSocketProtocol docstring.
In gui/protocol.js create a simple method for debug logs.
In gui/menu.html use the aforementioned method.
In protocol.js make sure the connection is closed at shutdown.
In gui.py, remove the GUI session file even when quitting abnormally
Ignore "exclude" setting for now

Users are notified on real time while they edit the contents of
the Settings window.

Report errors per field, check fields for completeness, warn
users with a dialog box when they want to save incomplete settings
and make the window prettier.

Also, stop saving settings when the window closes. The settings
are saved only if the user clicks on the "Save" button.