Added the new class Mail. This will represent a simple E-Mail. Can be
called and a new mail-Object will be created. The E-Mail address will be
checked and can throw an Exception which is logged. Have a look. Tried
to comment everything necessary. A Mail class will be useful in future
to store the Mails in a MailList, for example to display every mail
which was sended.
The class HelloWorld was renamed to MailTester to check the Mail class.
Configured the logging which can now used and the logging will be
printed out in the console.