`CsvDataSource` should throw exceptions on error

[sebastian-peter]

CsvDataSource returns empty stream/set on error, which does not seem to make much sense.
It seems to me that the input file not existing can be fine (a lot of input sources are optional), but errors during reading and parsing of csv files should still escalate and not just produce an empty stream.

Methods: distinctRowsWithLog, buildStreamWithFieldsToAttributesMap (2x)

Don't forget to adapt JavaDoc.