Support more map output key types. #2
Description
At least:
• BooleanWritable
• BytesWritable
• ByteWritable
• DoubleWritable
• FloatWritable
• IntWritable
• LongWritable
• NullWritable
• Text
• UTF8
• VIntWritable
• VLongWritable
• HBase KeyValue….
• Hive HiveKey…..