Get rid of compose header

It is duplicative of window header and takes up substantial screen real
estate.
IMP_Compose#replyMessage() now returns address objects instead of strings.
IMP::parseAddressList() now supports Horde_Mail_Rfc822_List objects natively
phpdoc
Don't return headers array from IMP_Compose#forwardMessage()
Draft resuming methods no longer return headers array
Pass reply addresses to dynamic views as an array instead of a string