implement JsonSerializer
add EntityDocumentSerializer
	JsonSerializer
	JsonProcessor
	createItemDocument method in TestObjectFactory
	JsonSerialisationExample
add licence header
add javadoc to the example
Merge remote-tracking branch 'origin/master' into json-serializer
fix confilict
	- name MWDumpFileProcessorImpl to MWRevisionDumpFileProcessor
	- remove unused imports
update sitelinks in ItemDocumentEntry.txt
Merge remote-tracking branch 'origin/master' into json-serializer
add qualifiers-order attribute to ItemDocumentEntry.txt
restructure JsonSerializer
	- remove JsonProcessor and integrate this functionality into
JsonSerializer
	- change the interface for EntityDocumentSerializer
	- compressed output in the example
Various smaller fixes

* Fixed Java warnings
* Fixed spelling errors in names and comments
* Simplified code in some places
define UTF-8 encoding
writeEntityDocument methode to reduce code redundance
linebreaks after each document
change testcode
Small fixes

* Close stream after use
* Use StandardCharsets to get UTF-8 charset
* Throw something when catching an IOException during serialization
Update RELEASE-NOTES.md
Merge pull request #64 from Wikidata/json-serializer

Json serializer
Merge remote-tracking branch 'origin/master' into dump-processing-pipeline
Adopted example code to use new processing controller

(and fixed processing of property documents, which was missing)