Fix #2. Refactored aggregations/group bys; added SUM.

Aggregations and group-bys were linked; this patch decouples them,
fixing bug #2.

Also adding SUM and REDUCE as queries.
ASDF-ing up the files.

Keywordized the DSL clauses. Renamed SELECT to CL-LINQ-SELECT to
minimize collision chances.

Also added test query for funzies.

This set of changes is validated to load locally on my Quicklisp
instance.