make all implementations of getDataSet() throw DataSetInstantiationException
rename DataSetInstantiationException to DatasetInstantiationException (no more camelCase)
rename DataSetContext to DatasetContext (no more camelCase)
rename DatasetContext.getDataSet() to getDataset(); keep old one as deprecated
small simplification
also rename DataSetInstantiator
remove legacy getDataSet() instead of deprecating it
Merge branch 'feature/get-ds-exceptions' into release/2.6.0