PARQUET-79: add a streaming Thrift API, to enable processing the metadata as we read it and skipping unnecessary fields.

This pull request provides an API to read thrift in a streaming fashion.
This enables ignoring fields that are not needed without loading them into memory.
It also aloow treating the data as it comes instead of when it's fully loaded in memory.
Seems the Consumers here is just used as a namespace. So should it be a package name?