Remove useless unit tests.
Use 'ICONS' as default toolbar style.

Since 'gtk-toolbar-style' is deprecated, apparently meaning that
application authors should choose.

https://developer.gnome.org/gtk3/stable/GtkSettings.html#GtkSettings--gtk-toolbar-style
Remove useless unit tests.
Fix toolbar style initialization.
Don't cancel, but accept editing on cell renderer focus-out.
Rename interactive test methods.
Make sure length unit change changes multiline renderer text.
Rearrange methods.