Add metadata abstraction for ORC
Fixup metadata abstraction

Rename Stream.Kind to StreamKind
Rename Type to OrcType
Rename Type.Kind to OrcTypeKind
Rename ColumnEncoding.Kind to ColumnEncodingKind
Extend custom ORC reader to support DWRF
Add OrcPredicate abstraction

Move TupleDomain filterint to TupleDomainOrcPredicate
Add ORC test for column of nulls
Add ORC file format description
Fixup BenchmarkHiveFileFormats