(Paris2013) Initial work for PP images in activities.
(Paris2013) Adding multiple content items for content-related items
(Paris2013) Switch 'medium' to 'normal' for page previews.
(Paris2013) Add oae-threedots for the overlay link. Don't show mini-thumbnails for non-files
(ActivitiesPP) Cropping preview height, fixing comment indentation.
Merge pull request #2595 from mrvisser/activities-pp

Adding Content Previews to Activity wall.