Blog has ∞ scroll, plus feature revert

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#2813: Open embed.ly providers link in new tab.
Embed files have no download link #4766
Add setting to disable using default image for the people page.
Work on default image UI for os profiles app.
Work on UI for os_profiles app settings.
More work.
More work.
Add display style examples.
Add view mode "no_image_teaser" for a profile.
Fix sidebar teaser preview.
Add checkbox to disable default image.
Cleanup.
Fix logic and comments.
Avoid affecting widgets.
Make people term pages affected by the os_profiles app settings.
Merge pull request #5039 from openscholar/4814-1

Code cleanup and fixes.
Cleanup.
Merge branch '4814-1' into 4814
Add tests for changing display type for os_profiles.