Ensure that blueshirts can't see pending emails either.

Since the addition of the PendingEmail support, blueshirts attempting
to view the details of users (that they could administrate) which
had an outstanding email change would have got a 500 error.
This fixes that error, and also prevents the blueshirts from seeing
either email address (as is intended).

Change-Id: I388d30c408f7d2298c65b6e6f25d8e968523f064
Let some blueshirts see (limited) details of all competitors

This changes user detail fetching to using the can_view mechanism
of libnemesis, which has slightly more generous restrictions on who
can see what data. This needed to enable the reception desk at the
competition.

Change-Id: I1a10297b07c7f522d7ca96fe88a5863419154383