Parquet index

[shay1bz]

Summary

Adding the option to have Parquet index, instead of Avro btree. This is for batch-only use cases, where fetches are rare or not used at all. In such cases, in large scale, Avro index performance is (or at least should be) inferior to Parquet especially when filtering or projecting columns.

In this implementation the index type (avrobtree/parquet) is stored in the index table props, and fetch throws UnsupportedException under parquet index.