Parquet Combine Input format for MapReduce job

ParquetInputFormat can only process one parquet file, if there are small files, it will spawn many small map task processing the small file. It is not efficient.
We need to provide CombineInputFormat to combine small files together in one map task.

**Reporter**: [Bing Jiang](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=jiangbinglover)

_{**Note**: *This issue was originally created as [PARQUET-1051](https://issues.apache.org/jira/browse/PARQUET-1051). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Start by reading the ParquetInputFormat entry point and the MapReduce input-format behavior described in the issue. Determine how small Parquet files should be combined into a single map task, then verify that the resulting input format processes those files together without losing records.

Scritto dal modello di indicizzazione a partire dal testo della issue.