in-term: runs a program in *some* terminal

Set your preference by adding `term` somewhere in your path:

e.g.:

```
ln -s =rxvt-unicode ~/bin.local/term
```
ensure-in-term: execs a terminal if not in one

See usage in next commit w/ vpn changes
vpn: reworks to use openconnect (not nmcli)
mon: fixes syntax (near-)error
mon: adds --single = turn off all ext monitors
vpn: adds optional certificate from ~/.config

If ~/.config/vpn.$host.crt exists, its SHA1 fingerprint will be passed
to openconnect.  (This allows the use of self-signed certs, provided you
download it beforehand.)