qtutils: refactor widget save/restore methods into the base classes

Move all of the qtutils functions related to saving and restoring widget
state into the widgets.standard base classes.  This means that
widgets.standard no longer depends on qtutils, and qtutils no longer
depends on settings.

Signed-off-by: David Aguilar <davvid@gmail.com>
merge: use the mac metal style on OS X

Signed-off-by: David Aguilar <davvid@gmail.com>