Fleshed out the JsonDumpFileProcessor.
Speedtest finetuning
Merge branch 'externalJsonReader' of https://github.com/Wikidata/Wikidata-Toolkit into externalJsonReader

Conflicts:
	wdtk-dumpfiles/src/main/java/org/wikidata/wdtk/dumpfiles/json/JsonDumpFileProcessor.java
	wdtk-dumpfiles/src/main/java/org/wikidata/wdtk/dumpfiles/json/JsonLocalDumpFile.java