The number of values in a miniblock should be multiple of 32 instead of 8 in DeltaBinaryPackingConfig

In the code of [DeltaBinaryPackingValuesWriter](https://github.com/apache/parquet-mr/blob/master/parquet-column/src/main/java/org/apache/parquet/column/values/delta/DeltaBinaryPackingValuesWriter.java#L82), the parameters are always DEFAULT_NUM_BLOCK_VALUES(which is 128) and DEFAULT_NUM_MINIBLOCKS(which is 4). So if the file is written by parquet-mr, the number of values in a miniblock is always 32. It is consistent with the [spec.](https://github.com/apache/parquet-format/blob/master/Encodings.md#delta-encoding-delta_binary_packed--5)
However, the code in [DeltaBinaryPackingConfig](https://github.com/apache/parquet-mr/blob/master/parquet-column/src/main/java/org/apache/parquet/column/values/delta/DeltaBinaryPackingConfig.java#L41) indicates that the number of values in a miniblock must be multiple of 8. Would it be better if the limitation was changed to 32?

**Reporter**: [Shan Huang](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=shanhuang) / @shanhuuang

_{**Note**: *This issue was originally created as [PARQUET-2077](https://issues.apache.org/jira/browse/PARQUET-2077). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}