Fix email validation regex for email_admin_list, email_sender, and email_reply_to
Fix email validation regex for email_admin_list, email_sender, and email_reply_to

In a previous change mail_regex (string) was changed to a compiled re match object, which broke client side (JavaScript) validation of these config options.
frlen/simian,alexandregz/simian,frlen/simian,frlen/simian,alexandregz/simian,sillywilly42/simian,googlearchive/simian,alexandregz/simian,sillywilly42/simian,sillywilly42/simian,googlearchive/simian,frlen/simian,sillywilly42/simian,googlearchive/simian,selfcommit/simian,selfcommit/simian,googlearchive/simian,alexandregz/simian,selfcommit/simian,selfcommit/simian