Added notes for pg_trgm and PG slave service
Clarified documentation around the installation of the PostgresQL pg_trgm extension and its need to installed in the database and not just in the server instance.
Also added a section about installing the bitnami/postgresql chart with the slave.service.clusterIP=None setting to allow service discovery through kube-dns.
Signed-off-by: Gerard Hickey ghickey@gitlab.com