Support SQL arrays

Octo does not currently support SQL style arrays, but these are necessary for some client queries as well as for accessing some catalog table fields, such as the proargtypes field in the pg_proc system table. Accordingly, this feature should be implemented to support such queries.

A sample client query that uses the array feature is TSSCQ06.sql (keyword list truncated for brevity):

SELECT String_agg(word, ',')
FROM   pg_catalog.Pg_get_keywords()
WHERE  word <> ALL ('{a,abs,...,zone}'::text[])

A model for array behavior expectations is available in the PostgreSQL array documentation.