Update to properties in EventFacet from string to thing

[cyberinvestigationexpress]

This Pull Request resolves all requirements of Issue #375, changing computerName (string) to device (thing), and adding account reference.

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 (CASE/UCO) feature branch
• [x] CI passes in (CASE/UCO) current unstable branch (9f53459)
• [x] CI passes in CASE current unstable branch tracking UCO's unstable as submodule (merge-commit) (This was not the precise commit introducing the review, but the unstable UCO state is incorporated before this point)
• [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] Solutions Approval vote logged on corresponding Issue (once logged, can be taken out of Draft PR status)

[ajnelson-nist]

@eoghanscasey , FYI - there were a few owl:Datatype transitions that didn't happen. Fortunately, the OWL SHACL review mechanism caught them. You can see the catches by reviewing the "Correct X" commits in this PR.

[ajnelson-nist]

Converting to Draft until Solutions Approval vote is logged.