Add support for auto-partitioning in parquet writer

When a table is created with a partition by clause, the parquet writer will create separate files for the different partition values. The data will first be sorted by the partition keys, and the parquet writer will create new file when it encounters a new value for the partition columns.

When data is queried against the data that was created this way, partition pruning will work if the filter contains a partition column. And unlike directory based partitioning, no view is required, nor is it necessary to reference the dir* column names.