Allow incoming "Forward" mails to open chat automatically with original sender

[hpk42]

If I use a delta account (say with a DELTA e-mail address) i want to specify a ROOT e-mail address from which Delta will process forwarded messages as if the forwarded message had arrived to DELTA directly, with the ROOT e-mail address replaced by the DELTA one. This means:

• the original sender is accepted as a contact

• all participants of the original message are members of the implicitely created group chat (it should be a group chat because during the chatting the original sender may add CCs or we might want to add another person)

• the original message will appear in the chat (there should be an indication that this chat resulted from a forwarded message)

As to the ongoing discussions in the various "Subject" header related issues, it would be nice if when posting to this implicit chat, the subject line would not be "Chat: " but rather the typical "Re: " from e-mail clients.