DefaultTimeline: Don't show retweets from people we follow

We previously did this be just iterating through the current timeline
and not showing duplicate tweets, which was wrong of course if the
retweeted original tweet was not in the timeline anymore.
Since we save the friends array now we can actually to this in a
correct way.
Account: Implement follow_id and unfollow_id
pot update
Add friends test
DefaultTimeline: Small whitespace fix
ProfilePage: Add/Remove user id from friends list
HomeTimeline: Don't remove tweet we don't add

We did the same thing for start up tweet batches.
HomeTimeline: Show retweets when we hide tweets from a user
Timeline: don't show retweets from users themselves