Mutt: move sensitive data out into separate config
Mutt: forward *with* attachments

Something I thought Mutt somehow can't do: forward messages including
the original attachments. It was such a pain to do this manually, and
now it's gone, thanks to
https://tdi.github.io/2014/09/12/forwarding-messages-with-attachments-in-mutt/
Mutt: add macro that deletes the thread marking all as read
Mutt: little cosmetic tweaks to config file