Modify query_error() to log errors to a database table instead of displaying them on the screen. This should

let us more easily debug difficult or intermittent issues that users may not report. Add a cron to report logged
errors to appdb admins every night.  Implement some basic unit tests for the new error logging code

unit_test/run_tests.php

@@ -12,5 +12,7 @@ echo "\n";
 include_once("test_query.php");
 echo "\n";
 include_once("test_image.php");
+echo "\n";
+include_once("test_error_log.php");
 
-?>
+?>