Refactored query engine to have different processing pipeline for raw queries. This enables queries that have a large offset to not keep everything in memory. It also makes it so that queries against raw data that have a limit will only p
rocess up to that limit and then bail out.
Raw data queries will only read up to a certain point in the map phase before yielding to the engine for further processing.
Fixes#2029 and fixes#2030
Paul Dix