Add "has ESCO/ O NET code" data property

[giacomodecolle]

Describe the bug
As described in the FOIS 2023 paper pp. 6-7, ESCO and O NET terms should be related to OccO classes by using new OccO data properties.

Expected behavior
Data properties relating OccO terms to ESCO and O NET, as described in the FOIS 2023 paper pp. 6-7, are added to the .owl file.

[zhengj2007]

Can anyone provide the ESCO codes that associated with the OccO occupation holders?

Current we only have US SOC ID in the ontology.

[giacomodecolle]

@zhengj2007 Hi, I was not suggesting that we should add ESCO codes for a specific class, but rather that we should add the data properties needed to relate classes to ESCO/ SOC codes.

[zhengj2007]

@giacomodecolle It is a kind of mapping of OCCO terms to ESCO/SOC codes. I am thinking to use annotation properties rather than data properties.