Configure mail session properties

[marcelmay]

Support configuration of default custom mail session properties protocol/service.

• Mail session properties will be used as default whenever applicable
• Mail session properties can be set per protocol
• Example properties include overall or protocol specific properties (e.g. SMTP)

GreenMail greenMail = new GreenMail(new ServerSetup[]{
        ServerSetupTest.SMTP,
        ServerSetupTest.IMAP.mailSessionProperty("mail.imap.minidletime", "100")
});