Move more properties to the "Glossary"; rename to "Core Concepts"?

[roll]

Overview

As a consequence of the organic growth of the Standard usage we got a situation where we reference some properties from other specs e.g.:

• resource.contributors -> package.contributors
• https://github.com/frictionlessdata/datapackage-v2-draft/pull/63
• etc

We just need to move common ones into the Glossary and reference them from there