增加显示邮箱目录,显示最新邮件数,打开别的信箱如发件箱三个功能

使用方法:
        $mailbox = new ImapMailbox($mailLink, EMAIL, PASSWORD, ATTACHMENTS_DIR, 'utf-8');
	$mailbox->listmailbox();
	
	//get new count
	$newcount=$mailbox->countNewMails();
	echo "你有".$newcount."封新未读邮件<br>";

        //get outbox count
        $mailbox->reopen('Sent Messages');
        $newcount=$mailbox->countMails();
        echo "你发件箱有".$newcount."封邮件<br>";

返回结果:
Mailboxes
INBOX
Sent Messages
Drafts
Deleted Messages
Junk
你有3封新未读邮件
你发件箱有2封邮件