ComputationHandler and GeospaceHandler

This change adds the concept of a ComputationHandler, designed to perform computations for computed columns from one or more source columns during ingress / upserts.   It also adds a handler for Geospace / geo region coding of point columns that are ingressed.
This comment is in the context that we are going to change sourceIt to Iterator[Map[String, SoQLValue]] : can we also make this method just return a SoQL type? I don't think the computation handler should have to know the name of the column it's computing and be responsible for  adding the new SoQLType to the map. This shold be external to ComputationHandler.