Add pgsql IDL
Started on actual extension
Stub impl of Postgres extension
Add Postgres to CMake
Adds initial result fetching.

This also moves the state of development into "usable - just",
since you can now actually do basic database stuff.
Improve field name conversion message
Add affected_rows
Add extra paths to PGSQL cmake file
Handle connection failures in pgconnect
Add more querying functions

Adds more of the querying functions. Plugs a few leaks.