CDM WIKI - Foreign Key?

[ericaVoss]

When the CDM Wiki calls out that you can look up concepts in the Vocabulary, particularly when it mentions "foreign key" the Wiki should give the Vocabulary or domain.

[clairblacketer]

I also think it may be good to add some example queries where appropriate

[clairblacketer]

related to #151

[vojtechhuser]

As we improve this, we should author Heel rules that check this.

[clairblacketer]

added in v6.0