Parquet OutputFormat should allow controlling the file size

To generate the most efficient on disk file, the size of the file is important to control. It would be nice if we could configure the ouputformat to roll over new files when it reaches the right size and start a new file.

There's currently no easy way to tune this and requires indirect tuning (number of reduces, map input size).

**Reporter**: [Nong Li](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=nongli) / @nongli

_{**Note**: *This issue was originally created as [PARQUET-17](https://issues.apache.org/jira/browse/PARQUET-17). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

The issue names the Parquet OutputFormat but no files or tests. Start by locating that entry point and determine how output file sizing is currently handled; done means exposing a configurable size threshold that rolls output into a new file when reached.

Written by the indexing model from the issue text.