enforce unique mail_access source/type

interface/web/mail/form/mail_blacklist.tform.php

interface/web/mail/form/mail_whitelist.tform.php

interface/web/mail/lib/lang/ar_mail_blacklist.lng

interface/web/mail/lib/lang/ar_mail_whitelist.lng

interface/web/mail/lib/lang/bg_mail_blacklist.lng

interface/web/mail/lib/lang/bg_mail_whitelist.lng

interface/web/mail/lib/lang/br_mail_blacklist.lng

interface/web/mail/lib/lang/br_mail_whitelist.lng

interface/web/mail/lib/lang/ca_mail_blacklist.lng

interface/web/mail/lib/lang/ca_mail_whitelist.lng

interface/web/mail/lib/lang/cz_mail_blacklist.lng

interface/web/mail/lib/lang/cz_mail_whitelist.lng

interface/web/mail/lib/lang/de_mail_blacklist.lng

interface/web/mail/lib/lang/de_mail_whitelist.lng

interface/web/mail/lib/lang/dk_mail_blacklist.lng

interface/web/mail/lib/lang/dk_mail_whitelist.lng

interface/web/mail/lib/lang/el_mail_blacklist.lng

interface/web/mail/lib/lang/el_mail_whitelist.lng

interface/web/mail/lib/lang/en_mail_blacklist.lng

interface/web/mail/lib/lang/en_mail_whitelist.lng