v8.0.0-beta.3

JSON Schema draft2012-12 support - prefixItems, new semantics of items, dynamicRef and dynamicAnchor

Fixes:

• #815 - incorrect resolution of $ref: "#" with $id in subschema
• #1493 - incorrect error message for missing property with ownProperties: true option
• #1501 - incorrect compilation of JTD schema with many properties in the schema