Adds a reasonably feature complete implementation of full text search
using the built in PostgreSQL engine. It uses public APIs from
Expression and Lookup.
With thanks to Tim Graham, Simon Charettes, Josh Smeaton, Mikey Ariel
and many others for their advice and review. Particular thanks also go
to the supporters of the contrib.postgres kickstarter.
Simon Charette
Claude Paroz
Matthew Somerville
Marc Tamlyn
Thomas Chaumeny