lightweight_activity#serialize_for_portal  include thumbnail_url

"When an author adds a thumbnail to an **activity** the image will be
displayed next to the listing for the activity in the Browse
Instructional Materials section of the portal."

Lara side of : [#57993872]
https://www.pivotaltracker.com/story/show/57993872
Fix failing publication_controller_spec.

https://travis-ci.org/concord-consortium/lara/builds/22804280
Remove rogue console.log
Remove reference to lab.iframe-phone.js (built in now)