publish ap-voc as ttl

[VladimirAlexiev]

Is your feature request related to a problem? Please describe.
Turtle is a better serialization than RDF/XML because it's more readable.

• ap-con (SHACL constraints) are given in Turtle
• but ap-voc (ontologies) are given only in RDF: ap-voc/rdf

Describe the solution you'd like

• Add ap-voc/ttl and a Makefile to regularly make them from RDF
• Unless there is some clear logic in the sequence of terms: sort them alphabetically for easier reading/finding; of course prefixes and owl:Ontology should come first

Describe alternatives you've considered

• riot --formatted=turtle is a good way
• Sorting of terms is easy to do with perl, I've done it many times

[VladimirAlexiev]

Done: https://github.com/Sveino/Inst4CIM-KG/tree/develop/rdfs-improved/CGMES-NC/ttl