Allow checkout panes to have a configurable title

I’m customizing our checkout flow pretty heavily, recreating a bunch of the panes. One thing that would be nice is to allow a public facing ‘title’ attribute for panes instead of just relying on the pane's label. Currently there’s just the label which is displayed in the in the pane row in the admin manage workflow page, and also as the title of the checkout pane during the checkout process. I duplicated a couple of the panes, and I changed the label to ‘{Company Name} Order Information’ so that we could differentiate them on the manage workflow page. I was able to set ‘#title’ manually in each pane, but that doesn’t work for the Review pane.