Broken links and formatting problems in Parquet documentation

The links to LogicalTypes.md and Encodings.md in [the Parquet documentation](http://parquet.apache.org/documentation/latest/) are broken. That page also has what appear to be some Markdown formatting issues:
- multiple lists are rendering incorrectly: the list of types under the "Types" header, the list of data under the "Data Pages" header, and the list of extension points under the "Extensibility" header
- some underscores that should be escaped are instead rendering as italics - see the last line under the "Nested Encoding" header

**Reporter**: [Roland Crosby](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=rolandcrosby)

_{**Note**: *This issue was originally created as [PARQUET-1161](https://issues.apache.org/jira/browse/PARQUET-1161). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Commencez par la page de documentation de Parquet liée dans l’issue et examinez les références à LogicalTypes.md et Encodings.md. Vérifiez les sections Types, Data Pages, Extensibility et Nested Encoding pour rechercher les problèmes de rendu Markdown signalés. C’est terminé lorsque les liens fonctionnent et que les listes et les underscores sont rendus correctement.

Rédigé par le modèle d'indexation à partir du texte de l'issue.