Domain delete should delete domain aliase

[JohannesM]

https://github.com/Exim4U/src/blob/master/home/exim4u/public_html/exim4u/sitedelete.php#L31
If the sitedomain has aliase, the aliase will not be deleted. Next time you create aliase that existed before, you can't create them because they are still in the database.

Steps:

1. create local domain (foobar.com)
2. create domain alias (foobar.net -> foobar.com)
3. delete local domain (foobar.com)
4. create local domain (foobar.com)
5. create domain alias (foobar.net -> foobar.com)
6. Error: can't create domain alias.