[feature request] Progress Bar should include Preview step

[mschfh]

Are you requesting a feature, reporting a bug or asking a question?

Feature Request

What is the current behavior?

The progress bar/TOC only shows question pages.

What is the expected behavior?

The progress bar should have an option to include "Preview" (if showPreviewBeforeComplete is configured), as that is another page/step being shown before the form is submitted.

How would you reproduce the current behavior (if this is a bug)?

    "showPreviewBeforeComplete": "showAnsweredQuestions",
    "showProgressBar": "top",
    "progressBarType": "pages",
    "progressBarShowPageTitles": true,
    "progressBarShowPageNumbers": true

[tsv2013]

@mschfh Thank you for the suggestion. I've added it to our backlog.