Use of evidence codes

[mcourtot]

Should the evidence in the example at https://github.com/phenopackets/phenopacket-format/wiki/Tutorial be relying on the ECO codes, such as instead of having

    evidence:
      - types:
          id: TAS

this should be

   evidence:
      - types:
          id: ECO:0000033
          label: traceable author statement

[balhoff]

I think so. This is actually highlights a problem with expectations for use of the JSON-LD context: unprefixed terms in "value position" cannot be expanded in that way. There is some more information in #40.

[balhoff]

Turns out I was mistaken about the possibilities for expanding terms in value position. I commented on #40.