Fix column order issue in cast
Previously, the order of the columns in the features passes to `cast_` mattered.
However even though features passed to `cast_` had the same order as the dataset features, it could fail because the schema that was built was always in alphabetical order.
This issue was reported by @lewtun  in #623 

To fix that I fixed the schema to follow the order of the arrow table columns.
I also added the possibility to give features that are not ordered the same way as the dataset features.