CDK-540: Handle other GenericRecord implementations in FileSystemDatasetReader

 * FileSystemDatasetReader now handles other implementations of GenericRecord
 * HBase won't handle them, but that is not a regression and will be fixed in
CDK-541.
 * Added a test for CSVFileReader.
Merge pull request #147 from joey/fix_type_for_read_generic

CDK-540: Handle other GenericRecord implementations in FileSystemDatasetReader