validation issues with ICF CodeSystem

ICF CodeSystem has validation issues. In particular:

- Quite a few concepts (mostly near the end of the JSON file) have no code
- Codes provide values for a `uri` property, but this is not declared. Probably should be `icd11-uri`, which is declared but never used

I also noticed there is also some weirdness in the hierarchy - there are a bunch (actually, quite a lot) of codes that appear as children of "BlockL2-s81 Skin and related structures" that do not belong there (in that they are not skin and related structures codes). This is not a validation problem, but its a bad smell.