check for new dump via cronjob

[nichtich]

• load DCAT-AP into rdfstore (or rdflib.js or another JS RDF library) and query for latest dump file and its byte size
• check the dump file does not exist locally yet with the same byte size
• make sure there is enough space on hard drive
• download file
• exit with success to trigger processing afterwards

such download script might also be put into wikidata-filter