purl-next: Extend the PURL JSON test suite to support ecosystems

[pombredanne]

As part of the PURL standardization process and the refactoring the spec for each package type in a structured schema data, we are also expanding or creating PURL JSON test suites to support for the supported ecosystems to better enforce conformance and ensure all tools behave the same.
The JSON test suite ensures that tools can use the same tests. This to enhance tests for the registered PURL types.

[pombredanne]

This is now merged with:

• Refine Purl type schema package-url/purl-spec#514

See also the subissues for a summary:

• purl-next: Create new JSON schema for PURL tests #3
• purl-next: Extend the PURL tests for registered PURL types #4