Remove symbolUnicode and symbolHtml? (post-531 implementation)

[rjyounes]

Note: these predicates do not currently exist, but will exist after the implementation of issue #531. #531 involves renaming to make them applicable to things other than units. This is about whether we need the HTML and Unicode versions of the symbol predicate.

[uscholdm]

I thought we agreed to keep Html and Unicode versions based on what @Jamie-SA said about the likelihood of using them in the foreseeable future. See #531 and #959.

[rjyounes]

I didn't think we reached a conclusion on this. There is the possibility of implementing them in the SA ontology. It depends on whether we consider the need for them broad enough to include in gist.

[sa-bpelakh]

Recommendation: Move HTML/Unicode to SA ontology, remove from core. Verify with @Jamie-SA

[rjyounes]

Assigning to @Jamie-SA for review. If he approves, he can either implement or pass on to someone else.

[Jamie-SA]

Yes, approved.
We can add them to one of our domain ontologies if you don't want them in gist.