handle hets-error where a file isn't an ontology

This is specifically targeted on catalog files.
Hets now returns a specific error message if
an 'ontology'-file is in unknown xml format,
so it probably isn't an ontology.
raise minimal hets version to 18564

This is needed for hets throwing the correct
error message on catalog files.
add spec-helper method to parse a specific file.
move the error-handling into the hets module.
add a spec for non-ontology-file decision.
do not update state on destroyed ontology

We need to 'abort' the do_or_set_failed block.
Merge branch 'staging' into 776-declare_file_as_non_ontology

Conflicts:
	config/hets.yml
Merge pull request #801 from ontohub/776-declare_file_as_non_ontology

776 declare file as non ontology