Hooked up participant cap

We’re now displaying <numberOfAttendees + 1 (for
coordinator>/<max_participants> in each study card. This may not be the
most meaningful way of displaying this information, but we can always
tweak it later.

I also wrote a client-side filter to hide all full study sessions from
the (newly renamed) Find Sessions tab. They will still show up in the
hosting/attending tabs, however. I decided against doing this server
side, since we’re only making one database call to return all sessions
for Find/Hosting/Attending and refactoring this would have been fairly
non-trivial.