Reference tables, prepared statements, more SQL

Second release candidate for 6.1.0

Initial candidate for 6.1.0

pg_upgrade compatibility and minor bugfixes

PostgreSQL 9.6, colocation, better SQL, txns, FKs

Tweaks config, fixes bugs, adds IF INDEX EXISTS

Candidate for 6.0 release

Subquery pushdown and memory leak fixes

Schemas, SERIAL, RETURNING, transactions, more SQL

Candidate for 5.2 release