Minor discrepancies between Metadata spec (v 1.0) and the JSON schema

[ilsley]

Here are few apparent discrepancies:

• The Metadata spec requires DIFFERENTIATION_METHOD for Cell Line. This is not required in the JSON spec.
• Metadata spec has DONOR_HEALTH_STATUS_ONTOLOGY_URI as a required property. The JSON spec (v 1.0) apparently has a misspelling: _donor_health_statusuri instead of _donor_health_status_ontologyuri.
• sample_ontology_curie and disease_ontology_curie are required fields in v 1.0, but according to #71 they should be URI not CURIE. (The relevant properties defined in the schema are _sample_ontologyuri and _disease_ontologyuri.)