this entails a couple of breaking changes due to schema evolution. once
the schema is stabilised, backward compatibility promise will be given.
* update config struct and accompanying scructs
* update tests
* update exampleConfig.dhall
* update local dev environment (devenv)
* make settings reflect the config schema changes
* make use of some settings/config updates
the Dhall config package formerly in ./config/schema has been moved to
https://git.dotya.ml/mirre-mt/pcmt-config-schema/, meaning the schema
has been decoupled from this repository.
the schema is now being versioned, which makes it easier to progress
without breaking stuff (unless we wanted to reference the versions by
commit hashes...).
* use schema version 0.0.0
