Rename Views method default_not_found() to defaultNotFound()

Taking this with baldwinlouie.

Patch attached. Tested with a view that has a path, looks for a contextual filter, and has the contextual filter setting of "Page not found" when there's no argument. Test view is (correctly) page not found where there's no argument, tries to show a view if there is an argument.

+++ b/core/modules/views/lib/Drupal/views/Plugin/views/argument/ArgumentPluginBase.phpundefined
@@ -691,7 +691,7 @@ function default_ignore() {
+  function defaultNotFound() {

Add public access modifier in front of the function to adher to the new OOP standards.

Shouldn't that be better protected?

@dawehner: i wasn't sure in which context a method like that would be called, which is why i suggested public before.

It's called in ArgumentPluginBase::default_action()

Re-rolled with protected.

#9: 2002460-rename-default_not_found.patch queued for re-testing.

Committed e44d062 and pushed to 8.x. Thanks!