Some more tests. Added equals(), hashCode() and toString() to DatatypeId
Added Logging to datamodel.
Changed Logging bindungs to slf4j-api to leave the choice of which
concrete logger to use to others.
Also fixed minor issues with the StatementImpl
Changed the behaviour of DatatypeId to throw an exception when
encountering an unknown datatype, instead of just logging an error.
Added support for Monolingual text datatypes (also in the JSON dumps)
Removed slf4j-api (dependency provided by parent.)
Fixed Issue with maven build not passing due to a faulty test that
standalone jUnit, for whatever reason, let pass.
Added further testing.
Tested MonolingualText data values. Fixed related bug.
Some more test coverage.
Disable speedtest for CI
Automatic code layout fixes
Merge branch 'externalJsonReader' of
https://github.com/Wikidata/Wikidata-Toolkit.git into externalJsonReader

Conflicts:
	wdtk-datamodel/src/test/java/org/wikidata/wdtk/datamodel/json/jackson/AllTests.java
Test language code registry
Renamed Jackson classes and added some documentation

More informative names also help to distinguish these classes from other
WDTK objects.

Documentation was added mainly for JacksonPropertyDocument.
Moved most Jackson classes into one package

Added package-info.java for documentation.
Reviewed and documented Jackson document implementations
Merge branch 'externalJsonReader' into cleaner-examples

Conflicts:
	wdtk-examples/src/main/java/org/wikidata/wdtk/examples/DumpProcessingExample.java