[misc] calcurse-caldav CALCURSE_CALDAV_PASSWORD security


calcurse-caldav currently accepts the caldav password through the environment

This is [marginally more secure](https://stackoverflow.com/q/12461484) than
just sticking it in a text file, as `/proc/$pid/environ` will contain the
password passed through.

Is the purpose of this feature for security? Or is it just a convenience to use
with a password manager?

I would hope to see something like "caldav password command", which the
application then runs itself and stores the password in it's own memory (which
arguably can still be recovered, just harder)

I'de be willing to work on implementing that feature if it sounds like a good

Thanks a lot,

Marco Sirabella