Add datafusion feature

[westonpace]

Datafusion already has some initial Substrait support but it does not yet handle extended expressions. When adding support for extended expressions upstream we may want to consider using substrait-expr to simplify the datafusion-substrait code. In addition, datafusion has some powerful features such as SQL parsing and expression optimization that we should expose. This feature should support:

• Datafusion import / export
• Datafusion as an SQL parser
• Datafusion as an expression optimizer