Add friends on Athlete.
Initial friends app, creates Friend requests from club members list.
Accept/Refuse friend requests.
Display friend status on profile page.
Fix friends listing.
When friends, allow full visibility.
Display friends sessions on session edit.
Display friends sessions on month calendar.
Send email on friend requests.
Display friend sessions on calendar when user don't have some too.
Add friends through requests to view their calendar, closes #92, closes #106.