Adding array support (waiting on merge in scala-records)

Discovered a bug in scala-records https://github.com/scala-records/scala-records/issues/100 & https://github.com/scala-records/scala-records/issues/101 preventing arrays/collections from being field values of records.

Potentially resolved, PRs: https://github.com/scala-records/scala-records/pull/102 & https://github.com/scala-records/scala-records/pull/103

Otherwise, this seems like it should deal with arbitrary arrays (primitives and not) as well as nested arrays. 
Internally the execution engine assumes that all arrays are actually of type Seq, so if we want to support this, I think we'll have to add some conversion on the input path as well.