New CSV transform feature

[grantnicholas]

Are you open to PRs?

I added in support to map multiple CSV files into a single parquet file in order to increase row group compression and decrease spectrum query times.

While mapping a single CSV to a single parquet file is a fine default for unloading full tables, for unloading partitions it tended to produce too many small parquet files.

[c-nichols]

Definitely open to PRs! This is something I thought about adding but punted on because it wasn't critical for our use.

[grantatspothero]

Awesome, I just opened PR #43 to add the feature.