Now the legacy drill.map.type and drill.report.filename are specified in this
way.
The BaseOutput class now inherits from Optionable.
Suboptions are just Optionable classes.
Also: added traceback print when an error is reported and we are in debug mode.
The --help-outputs and --help are embedded in the README.md
To make it easier to read now options are enclosed in `` and the list of
outputs is sorted.