Added ability to respond to synch queries for Redis

@anpete Both materialized and non-materialized queries now working. 

TODO: add same ability for asynch queries
The scan would have to be performed every time GetProjectionIndex() was called. It's already called a few times even for the relatively small queries and small number of customer "rows" I have in the tests. If there were many rows or more complicated queries it would be called many hundreds or even thousands of times. Hence I though pre-calculating it was better.