Changed settings and alert.py to no longer check the lvalert node against a whitelist of pubsub nodes.

Added user_is_internal to template context, so as to avoid showing links in nav bar to pages which are inaccessible

Added tests of eel creation for public, lvem, and internal users. EEL access is based on event access.

Added an ignore list of emails to which we should not send any response. The main reason for this is that I got into an email loop with Mailer-Daemon and produced a zillion files in my tmp directory.

Fixed problem with event creation and permissions. Need to do refresh_perms on both underlying and overlying event.

Added model level permissions on Guardian.GroupObjectPermissions for members of the executives group. Also restored a modified version of the ModelBackend that *doesn't* do authentication. This is so that the has_perm check on Models can work.