Decimal: Read/Write to parquet.

This adds support for the FIXED_LENGTH_BYTE_ARRAY parquet type and
encoding for decimals.

Change-Id: I9d5780feb4530989b568ec8d168cbdc32b7039bd
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1727
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins