use Locale.ROOT to make behaviour insensitive to I18n issues
cleanup messages
Added config to force tests to run using IPv4 to speed up tests.
Enable CombineFileInputFormat on avro & parquet

Enable Crunch's use of CombineFileInputFormat for Avro and Parquet
files (as CombineFileInputFormat can offer useful performance
improvements).
prevent potentially gigantic error messages in readCSV
Add Datasets#list to get a list of Dataset URIs.