Add methods for Friend Follower count discovery to FollowDAO

Also add active to queries that need it.
New Follower Comparison insight

Insight, templates, tests, added to all tests

Closes #2000
New insight: Diversify your links

Shows links you shared, and how many times

Adds a method to LinkDAO
Adds css for list of links in insight
Adds tests to suite
QA on staging: Run Diversify links today
Facebook Age Analysis Insight

Adds DAO methods for selecting commentors and favers.
Adds new tests to plugin tests.

Closes #1944