Twenty Seventeen: Featured image missing on front page

[celloexpressions]

You can set a featured image on the front page, but it isn't displayed anywhere. This is confusing UX and possible "loss" of content when switching an existing site to Twenty Seventeen. The image should still be displayed somewhere on the front end if it's set. It doesn't need to be hugely prominent, but should be there somewhere.

[karmatosed]

More in-depth discussion over on the GitHub issue: ​https://github.com/WordPress/twentyseventeen/issues/289. I've moved the discussion here as part of merge.

[laurelfulford]

Based on the discussion of a solution in GitHub, I added the front page's featured image above the front page content, similar to how it's handled in the other panels.

Also removed code that was setting the front page's featured image as a fallback to the custom header, and updated the conditions that add the has-header-image to remove reference to the front page's featured image.

[davidakennedy]

Iterates on 38402.patch and corrects comment for header class.

[davidakennedy]

In 38868:

Twenty Seventeen: Display featured image on static front page

This improves UX, since an image added will be displayed on front end as opposed to not at all. This fix added the front page's featured image above the front page content, similar to how it's handled in the other panels. Also it removed code that was setting the front page's featured image as a fallback to the custom header, and updated the conditions that add the has-header-image to remove reference to the front page's featured image.

Props laurelfulford.

Fixes #38402.