Decrease the default page size to 64k

Impala uses 64k for a page size and recommends smaller page sizes over the current 1MB default. We're considering an absolute minimum row group size of 1MB, so it makes sense to dial the page size down a bit.

**Reporter**: [Ryan Blue](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=rdblue) / @rdblue

_{**Note**: *This issue was originally created as [PARQUET-216](https://issues.apache.org/jira/browse/PARQUET-216). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}