Make it easier to send emails with Attachments

[Garethp]

At the moment, to send an email with attachments, it's required to first Create the item unsent, then Create and Attachment for that item, then Send the unsent item. Only the first part has an easy access method. We'll need the following methods

• createAttachments(ItemIdType $mailId, $attachments, array $options = array())
• sendItem(ItemidType $mailId, array $options = array())

As well as a

• sendMailWithAttachments($message, $attachments, array $options = array())

method