Rename reference mechanic in the Metaschema

[david-waltermire]

User Story:

As an OSCAL model developer, I need a clear indicator that a flag specified in a define-field or define-assembly is defined locally or globally. I would also like the feature used to reference global define-assembly, define-field, and define-flag to be consistent.

Goals:

• Rename @named to @ref in all assembly, field, and flag references. Also, use @name for locally defined flag elements within a define-field or define-assembly.
• Update all XSLTs used to generate schema, documentation, and content converters.

Dependencies:

#435 is related to this issue.

Acceptance Criteria

• All generated XML and JSON schema, content converters, and document generators are updated to reflect these changes.
• The Metaschema definitions are updated in a way that result in no changes to associated content.
• Documentation on the use of Metaschema is updated to fully document use of the @ref and @name features.
• No content is changed as a result of these changes.
• A single PR is approved that contains the above changes.

[wendellpiez]

Done in branch here; https://github.com/wendellpiez/OSCAL/tree/sprint22-metaschema

[iMichaela]

7/11/2019

This issue and the related ones (noted in #435 ) for the metaschema need to be reviewed together and unitested. However, more unit tests need to be created for the other features.

[david-waltermire]

This will be closed once PR #464 is pulled.

[david-waltermire]

This has been completed in PR #464.