Mockup related items pattern icons broken for Plone 4

This commit to mockup from some time back breaks Plone 4 compatibility for icons in the related items pattern:

https://github.com/plone/mockup/commit/e5b9169037a084558183b5a48ec773e2147ea2d1

I am working to harmonize plone.app.widgets 1.x to work with Mockup 2 per suggestions from @thet and others.

Thoughts about best place to remedy this?

Sean

The compromise:

(1) Plone 5 treats getIcon returned in JSON as a boolean, we can use this.

(2) For Plone 5, if there is an icon (getIcon === true), get icon (thumbnail) from image scales.

(3) For Plone 4, we are going to omit "type" icon just like Plone 5, but still want to have image thumbnails for Image type.

(4) There is a pull request that uses Plone 5 getIcon status and falls back to portal_type === "Image" for display of content image scale thumbnail (which just affects Plone 4). This pull request:

https://github.com/plone/mockup/pull/699

Incidentally, that PR has a few style tweaks for improved user experience when using the right-side browse button in result listings (more right margin to avoid scrollbar overlap, on-hover color for the button to delineate distinct action vs. item selection).

Sean