conditionally disable friend suggestion 'add' buttonr

...when !remainingFriendQuota && !freeToFriend

- also show a tooltip saying that the user is either free to friend or can't be
  friended because not free to friend when out of quota
add "suggested because friended you" reason
s/friend/suggestion
mock backend logic for friend quota, ui improvements
tooltip when friending a suggestion would count against limit

also css fixes