Recommend bcrypt passwords everywhere
Even though it is not part of nixos-mailserver, the fact that Radicale 3 does no longer support crypt passwords is a little pain point for people who want an integrated setup with contacts and calendars. Instead Radicale 3 asks for bcrypt passwords, which are luckily supported by dovecot2 directly, so no major user action is needed.
Since bcrypt is more secure than traditional crypt I have revamped the documentation to recommend bcrypt passwords everywhere.
Fixes #199 (closed)