Map-Reduce Support in Drizzle

Implement pluggable Map-Reduce operations on top of Drizzle (See Greenplum and AsterData implementations as a background reference point). The main reason this blueprint is here and not in Drizzle core is obvious: Map-Reduce is a data integration technology rather than a query processing one.
Note: This implementation of Map-Reduce will be very different from a Gearman based architectural approach presented at the 2009 MySQL Conference. It assumes that both Map and Reduce are database operations and that Map and Reduce nodes may form complex query execution graphs or trees.