Support writing to Avro files

Introduces support for writing tables stored as Avro files. This supports writing all
data types except TIMESTAMP. Supports the following COMPRESSION_CODECs: NONE, DEFLATE,
SNAPPY.

Change-Id: Ica62063a4f172533c30dd1e8b0a11856da452467
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3863
Reviewed-by: Victor Bittorf <victor.bittorf@cloudera.com>
Tested-by: jenkins