New Print Material from Post/Page

[mnelson4]

• [x] code it
• [x] link to items when print material already made
• [ ] document it (add a "design how-to" mentioning it, shortcodes, and CSS classes)
• [ ] make a video showing it (add a post to a project,, duplicate it, edit the dup, include it; alternatively, from the posts page, duplicate it, then add it to the project by filtering by print materials)