Automatically provide pref. domain quantizer
Implement rating predictor item scorer (#485)
Implement rescoring item recommender (#485)
add missing license headers
Update release notes
Merge rescoring recommender (closes #485)

Conflicts:
	lenskit-core/src/main/java/org/grouplens/lenskit/transform/quantize/Quantizer.java
	lenskit-predict/pom.xml
Add #485 to release notes
Make quantized rating predictor support null baselines
Bump JaCoCo version to snapshot (#466)
Re-enable Java 8 on Travis (#466)
Rewrite grouping cursor test in Java

Groovy and Java 8 have some problems with implementing iterators; this rewrites a test in Java to work around this problem (#466).