Submission Upload Email Fix

- fixed the Users::emailOptInUsers method to bring back a list of
"valid, opted in users";
- removed debug statements in submissionUpload and made success/error
messages from file uploads more user friendly
DocsMailer Reference Bug Fix

- removed the reference to DocsMailer.php in contactUs.php and
forgotPasswoed.php; the reference already exists in the Users.php class
which is loaded by the header.php template file