appnet, statusnet and twitter: Now a parent is provided in the notifications so threading of the mails will work.

* There was a problems with the notification mails. They need the parent, so that the mails are displayed threaded in a mail client. This is now added
* fbsync: Remove a link from the body if it is also the attached link and the link is inserted at the bottom of the body.
* appnet: In the past you couldn't answer to repeated items. This is now changed.