Statistic and Filter need a mechanism to get customized comparator from high layer user

As discussed in HIVE-10254, we might need a customized comparator from high layer user for generating statistic when writing and applying filter when reading.

The problem is that (use Decimal type in Hive as an example):
Decimal in Hive is mapped to Binary in Parquet. When using predicate and statistic to filter values, comparing Binary values in Parquet cannot reflect the correct relationship of Decimal values in Hive. This type mapping causes 2 problems:
1. When writing Decimal column, Binary.compareTo() is used to judge and set the column statistic (min, max). The generated statistic value is not correct from a Decimal perspective.
2. When reading with Predicate (also Filter), in which the expected Decimal value is converted to Binary type, Binary.compareTo() is used to compare the expected value and column statistic value. They are Binary perspective, and also the result is not right.

We could add an interface for customized comparator, and high level user like Hive provides the comparator to Parquet, since Hive knows how to decode the binary to Decimal and compare. Then Parquet could switch between customized and original comparison method.

**Reporter**: [Dong Chen](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=dongc) / @dongc
**Assignee**: [Dong Chen](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=dongc) / @dongc
#### Related issues:
- [Parquet PPD support DECIMAL](https://issues.apache.org/jira/browse/HIVE-10254) (blocks)

_{**Note**: *This issue was originally created as [PARQUET-281](https://issues.apache.org/jira/browse/PARQUET-281). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Beginne damit, den im Issue beschriebenen Pfad zur Statistikgenerierung für Schreibvorgänge und den Pfad zum Vergleich von Prädikaten/Filtern für Lesevorgänge nachzuverfolgen, und verwende HIVE-10254 als Referenz für das Verhalten von Decimal. Ermittle, an welcher Stelle ein High-Level-Comparator bereitgestellt werden könnte, ohne das bestehende Vergleichsverhalten zu ändern. Als erledigt gilt die Aufgabe, wenn ein benutzerdefinierter Vergleich Decimal-Werte sowohl in Statistiken als auch beim Filtern korrekt ordnet.

Vom Indexierungsmodell aus dem Issue-Text verfasst.