Adding dbpedia links whenever possible

[igrangel]

One of the main objectives of this work is to connect this knowledge graph with existing ones. Thus, in every case that links to wikipedia exist, there will be a corresponding dbpedia link, like in sto:IETF. When possible, please, add the links to dbpedia.

[sebbader]

We are currently working on automatic SHACL validations in another project. As soon as we have understood it sufficiently, I will add some shapes for STO, especially for these important annotations and links to LOD/DBpedia.