mod_authentication: send e-mails to all matching accounts, if and only if a username is set.

(cherry picked from commit ff8e9f77f19c8a33676ba03aa37d56ffe81ddb9f)
mod_authenticaton: fix input sizes for password, and e-mail/username fields.

(cherry picked from commit b756366ba97f450e4ba2486a3c326d145efdc098)