"device message" should not be a "forward" target, other forward issues

[r10s]

• when forwarding messages, "device message" is shown in the list, probably also other read-only chats.
  we should make sure, GCL_FOR_FORWARDING is applied correctly when getting the chatlist

• the forwarding list should also not start in "archive", even if the opened chat is in archive. this results in the same view always, and it is also more probable that one wants to forward to active chats

• the "cancel" button atop of the chatlist should go back to the original chat. i think, only on first display, when no subsequent chats were opened. so for the usecase the user hits "forward" accidentally and immediately cancels.
  later on, when the user has navigated back and forth, maybe even forgot what they wanted to do, this may be confusion, there, the current behavior seems to be fitting better (in theory, we can think about leaving the underying viewcontroller stay (so have chatlist -> chat -> chatlist), however, that needs probably adds more cornercases, makes things as "create chat by forwarding" harder, and probably is larger refactoring, so i would only change the cancel-button)

• when forwarding to "saved messages", we should also go to the original chat, see android. this is mitigated by the new "save" option, but still