update advanced preferences, fixes cmu-delphi#12

- update the list of required fields to reflect that some preferences 
are currently disabled
- fixes the bug where advanced preferences can't be updated

Author: dfarrow0

site/preferences.php

@@ -55,7 +55,7 @@ function createPreference(&$output, $label, $prefix, $name, $type) {
 $survey_fields = array('flu', 'vir', 'epi', 'ph', 'sml');
 $email_fields = array('reminders');
 // $advanced_fields = array('pandemic', 'leaderboard', 'initials', 'prior', 'hospitalization');
-$advanced_fields = array('pandemic', 'leaderboard', 'initials', 'prior');
+$advanced_fields = array('leaderboard', 'initials');
 $account_fields = array();
 ?>
 <div class="box_article centered">
@@ -299,16 +299,16 @@ function createPreference(&$output, $label, $prefix, $name, $type) {
                   For these reasons, the 2009 pandemic season is hidden by default.
                   However, forecasters who have experience in influenza epidemiology may find it helpful to display this atypical season.
                   Here you have the option to display the 2009 pandemic season on the chart alongside the more typical epidemic seasons.
-               </p> 
+               </p>
                <table cellspacing="0">
                   <?php
                   $prefix = 'advanced_';
                   createPreference($output, 'Show the 2009 pandemic', $prefix, 'pandemic', 'bool');
                   ?>
                </table>
                -->
-               
-<!-- Nobody gets data earlier than 2009, so don't ask 
+
+<!-- Nobody gets data earlier than 2009, so don't ask
                <p class="text_title left">Additional Seasons --- for National and Regional Forecasts</p>
                <p class="text_body left">
                   The flu sentinel surveillance network (ILINet) has been growing and evolving since its inception in 1997.