Add metadata abstraction for ORC
Extend custom ORC reader to support DWRF
Switch default file format to ORC
Make HiveRecordSink store uncompressed
Benchmark Hive input formats directly
Add support for NULL parition keys
Add support for TIMESTAMP in Hive partition key

Fixes #1474
Add Hive write support for varbinary, date and timestamp

Fixes #1425
Add HiveType.toString()