possibility to specify sender address for froxlor as the admin-email address, custom or empty for system-default; fixes #1217

Signed-off-by: Michael Kaufmann <d00p@froxlor.org>

install/froxlor.sql.php

@@ -686,7 +686,7 @@ opcache.validate_timestamps'),
 	('api', 'customer_default', '1'),
 	('2fa', 'enabled', '1'),
 	('panel', 'decimal_places', '4'),
-	('panel', 'adminmail', 'admin@SERVERNAME'),
+	('panel', 'adminmail', 'ADMIN_MAIL'),
 	('panel', 'phpmyadmin_url', ''),
 	('panel', 'webmail_url', ''),
 	('panel', 'webftp_url', ''),