Issue 536: Declare and warn of observable:File and :URL disjointedness

[ajnelson-nist]

This Pull Request resolves backwards-compatible requirements of Issue #536 .

Coordination

• [x] Pull Request is against correct branch
• [x] Pull Request is in, or reverted to, Draft status before Solutions Approval vote has passed
• [x] CI passes in UCO feature branch against develop
• [x] CI passes in UCO current unstable branch (0edff1b)
• [x] CI passes in CASE current unstable branch tracking UCO's unstable as submodule (b3fa35f)
• [x] Impact on SHACL validation reviewed for CASE-Examples
• [x] Impact on SHACL validation remediated for CASE-Examples (N/A)
• [x] Impact on SHACL validation reviewed for casework.github.io
• [x] Impact on SHACL validation remediated for casework.github.io (N/A)
• [x] Impact on SHACL validation remediated for CASE-Corpora
• [x] Impact on SHACL validation reviewed for CASE-Corpora
• [x] Milestone linked
• [x] Solutions Approval vote logged on corresponding Issue (once logged, can be taken out of Draft PR status)

[ajnelson-nist]

CASE-Corpora is impacted by this proposal, as it had drafted a few dataset-distribution objects trying to find the inconsistencies raised in Issue 536.

[ajnelson-nist]

CASE-Corpora issues have been remediated in its PR 56.

[ajnelson-nist]

The affirmative Solutions Approval vote has been logged. This PR can now be merged by anyone on @ucoProject/maintainers-uco but me (the filer).