[UX] Consider saving changes to custom block text without requiring a second save.

I understand the logic in that from a technical aspect in the workflow of saving layout changes (and being able to cancel those if required), but from an end-user experience point it is not that great. So...

Edit a layout, then edit a custom block and change its text. Save the block (it feels funny by the way that the button says "Save configuration", but lets leave that for another issue*). At this point, a new user would expect that refreshing the page that shows the changes they've just made in the backend would reflect those changes in the front end. That doesn't happen though. They need to return to the layout edit page (thinking that Backdrop "doesn't work") and then they see the "This form has unsaved changes." message that asks them to save the layout (#1656).

As I said, not optimal UX there.