lib/messageview: mark messages as read

Currently at least the notmuch and maildir worker only set messages as read
if a body part is fetched. The gpg abstraction however fetches the full message.

We can simply set the readstate when we create the messageview, avoiding the issue.

Once this is merged, we can cleanup both workers.

lib/messageview.go

@@ -91,6 +91,7 @@ func NewMessageStoreView(messageInfo *models.MessageInfo,
 	} else {
 		cb(msv)
 	}
+	store.Read([]uint32{messageInfo.Uid}, true, nil)
 }
 
 func (msv *MessageStoreView) MessageInfo() *models.MessageInfo {