Allow Settings view to be closed without saving
and without closing the whole window. For now it's only possible to tick the check mark here. Closing should bring a user back to the main window.
Another way is to give client the functionality that changes are always saved
e.g. see https://elementary.io/docs/human-interface-guidelines#always-saved
But then an providing an Undo would make sense as well #806
What do you think?