Version 1.6

This release modifies how certificate and private key paths are
interpreted. They are now searched for in $XDG_CONFIG_DIRS/litterbox,
i.e. in the same locations as configuration files.

The rc script for FreeBSD has been removed. The catsit[1] process
supervisor is now the recommended way to run litterbox on FreeBSD.

[1]: https://git.causal.agency/catsit/