fix expected direction of import links

If ontology O1 imports ontology O2, the import-link is actually
defined from O2 to O1 (O2 being the source and O1 being the target).
fix onto spec: switch source and target in setup
Merge branch 'staging' into fix_import_link_direction

Conflicts:
	spec/models/ontology_spec.rb
fix onto spec: source target switch
Merge pull request #766 from ontohub/fix_import_link_direction

fix expected direction of import links