Allowing for device-specific config file

- if "config/" is a dir, check there for a file named $OUTDIR, then "default"
- if "config" instead is a file, use that (as with v3 and earlier)
Allowing for an optional second parameter to adebar-cli

- this will be appended to the OUTDIR name for e.g. historization
- update docu accordingly
- moved config.sample to doc/ directory