Cleaner way to specify projection via builder

[Jefffrey]

https://github.com/datafusion-contrib/datafusion-orc/blob/4f1c98de1744033899f8f5a0c61a32eeffc5db25/tests/basic/main.rs#L21-L22

Bit clumsy to require the builder to create a projection which is then passed back to the builder

Find a cleaner way to do this