Enh/read parquet files

[rwblair]

trafficstars

Use hyparquet library to read read parquet files.Transforms them into a columns map, which may not be desirable. Parquet files have good typing metadata that is thrown away and this implementation, with everything becoming a string like when we read in TSV files. Type checking is then done via regex as per schema.objects.columns/schema.objects.formats entries.

Still need to implement maxRows.