SVN_SILENT made messages (after extraction)
Changing the type of reply from within the composer window

Gui: Change the reply mode from the compose window by means
of a dropdown menu from a tool button.

Switching to another (available) reply mode updates the recepients
list in the open compose window. If the "Hand Picked Recipients"
mode is picked, no action is triggered. Making manual changes to
recipients list reflects in the reply mode dropdown as a switch to
"Hand Picked Recipients" mode.

BUG: 321153
REVIEW: 118802
Support for forwarding messages as attachments

Allow forwarding of a message as an attachment by means of menu actions.
Forwarding takes care of mangling the subject line and marking the
original message as "$Forwarded".

Thanks to paalsteek for his initial work on this.

REVIEW: 118606
Tests: Add test to ensure setting of $Forwarded flag after a message forward
Tests: add test rows for reply subject mangling to handle "Fwd"s
Tests: add test for subject mangling when forwarding message