rafia_stpa_cli to use constraint directory specified in project.yml

rafia_stpa_cli --project ./stpa-sample.yml convert \
	--convert-trudag ./STPA-SAMPLE/constraints/ \
	--trudag-group STPA-SAMPLE-CONSTRAINTS \
	--trudag-reference stpa-describe

The project constraint directory is specified in the stpa-sample.yml project file.

This should be used, rather than repeated as a parameter.