Puts "Official" or "Contributed" next to ExternalActivity

…titles in search results list. [#49599765]

https://www.pivotaltracker.com/story/show/49599765
Always list official ExternalActivity before contributed.

[#49599765]
DRYing the last partial HAML a bit
Exemplars get a gold background.

[#49599765] Highlights the "exemplar" activities.

https://www.pivotaltracker.com/story/show/49599765