Displays per-camp fields to authenticated users.

Updates applicant info function to return both application info and user data.

Instead of returning either applicant_info or user data, the
thatcamp_registrations_get_applicant_info function returns an object
containing data from both the applicant_info and existing user data. This
helps with displaying values from both for when authenticated users fill out
the registration form.

Fixes #63.
Checks for empty $fields array.

Checks if the $fields array has something to display before echoing the
contents of the user info form.
Merge pull request #66 from clioweb/show-fields-logged-in

Displays per-camp fields to authenticated users.