Reset PURL Specification Documentation pages

[mjherzog]

Now that we have updated the documentation files in purl-spec/docs/standard to match the final text of ECMA-427 1st Edition we need to restructure the PURL Specification Documentation page(s) to match the structure and content of the updated documentation files.

[mjherzog]

The new structure for the PURL Specification page should be:

• Introduction - no change
• Specification (replaces Documentation title on the left-side index)
  • docs/standard/specification.md
  • docs/known-qualifiers.md
  • docs/how-to-build.md
  • docs/how-to.parse.md
• PURL Types
  • Keep current content at top
  • The current subsections: How PURL Types are maintained / How to Propose a New PURL Type seems to already match docs/maintain-purl-types.md, but it would be better to pull this text from the purl-spec repo
• Tests (new subsection) with text from docs/tests.md
• Schemas - OK as-is
• Adopters - Redirect to Software Specifications and Tools section of the home page.

[mjherzog]

@johnmhoran The key idea for this re-org is that we want the Specification page (currently labelled Documentation) to follow the pattern of the constituent documents so that there would be sub-sections or separate pages for:

• Specification
• How to build a PURL
• How to parse a PURL
• Tests

I am leaving out known-qualifiers.md for now because it does not fit the pattern well - it probably needs to be part of some broader scope document - otherwise it seems oddly specific.

PS - I have updated the 12/22 comment above to remove renaming the main section from Documentation to Specification.