This commit provides a working implementation of a ruby
type/provider (`postgresql_psql` for handling the PSQL
commands. This is a little more flexible than doing it
via Exec resources, which is what the `postgresql::psql`
type was doing.
The old type is still present but now includes a
deprecation notification, and all of the other types
that were using the `::psql` type have been ported over
to use the `postgresql_psql` type instead.
