Merge pull request #3798 from metabase/math-aggregations-part-1

src/metabase/driver.clj

src/metabase/driver/druid.clj

src/metabase/driver/druid/js.clj

src/metabase/driver/druid/query_processor.clj

src/metabase/query_processor/annotate.clj

src/metabase/query_processor/expand.clj

src/metabase/query_processor/interface.clj

src/metabase/query_processor/resolve.clj

test/metabase/driver/druid_test.clj