Fixed formatter example
[sql] Removed obsolete denormalizer file
[sql] implement provide_aggregate() with already prepared arguments instead of aggregate()
Convert cell (and split) from strings
[mongo] Changed to provide_aggregate()
[mixpanel] Changed to provide_aggregate()
[slicer] Use provide_aggregate()
is_aggregate is False for prepare_order() in members
[doc] Updated the aggregate()/provide_aggregate() documentation