Change ontology URI according to new naming scheme

Change URIs of all ontologies and entities in the KG from http://digitalheraldry.org/digital-heraldry-ontology/ to http://digitalheraldry.org/dho/ according to specifications in https://digitalhistory.atlassian.net/wiki/spaces/DHP/pages/2121531397/Schemata+von+IDs+im+Digital+Heraldry+Projekt