populate cache on sequence close
CachePopulatingQueryRunner -> CachingQueryRunner

Populate and use cache at compute node level
address code review comments
turn down too much logging; gp
Merge pull request #458 from metamx/stream-cache

use and populate cache at compute node level
fix npe in CachingQueryRunner
Merge pull request #473 from metamx/fix-caching-npe

fix npe in CachingQueryRunner
support dimension extraction functions in group by
Merge pull request #474 from metamx/groupby-dimextractionfn

support dimension extraction functions in group by