Add support for SQL schemas

It would be handy if something like this would be available:

```
$ pqrs schema --sql-dialect=clickhouse --name=ticker /path/to/file.parquet
CREATE TABLE ticker (
  isin String NOT NULL,
  O Int32 NOT NULL,
  H Int32 NOT NULL,
  L Int32 NOT NULL,
  C Int32 NOT NULL
) ENGINE = Parquet('/path/to/file.parquet');
```