* use GtkListBox to pack tweaks in
* use css themeing for more widgets

* set a list row background color
* set a minimum width for the sidebar

https://bugzilla.gnome.org/show_bug.cgi?id=705359

And also more consistent with the rest of the file.

Conflicts:
	gtweak/app.py

When self.get_austostart_condition() returns None and
autostart_type is not None, the following code will
try to apply split on None.
The exception handling catches this and returns the correct
value for the function in this case so it's harmless,
this just fixes so that there's no traceback in the application
output....

https://bugzilla.gnome.org/show_bug.cgi?id=702994

https://bugzilla.gnome.org/show_bug.cgi?id=656977