Add Patronis default postgres configs to the sample yml files (#1909)

This adds the default Postgres settings enforced by Patroni to the `postgres{n}.yml` files provided in the repo. The documentation does call out the defaults that Patroni will set, but it can be missed if you download postgres0.yml and use that as a starting point. Hopefully the extra commented out configs serve as a visual cue to save the next person from the same mistake :)

postgres2.yml

@@ -51,10 +51,15 @@ bootstrap:
       parameters:
 #        wal_level: hot_standby
 #        hot_standby: "on"
+#        max_connections: 100
+#        max_worker_processes: 8
 #        wal_keep_segments: 8
 #        max_wal_senders: 10
 #        max_replication_slots: 10
+#        max_prepared_transactions: 0
+#        max_locks_per_transaction: 64
 #        wal_log_hints: "on"
+#        track_commit_timestamp: "off"
 #        archive_mode: "on"
 #        archive_timeout: 1800s
 #        archive_command: mkdir -p ../wal_archive && test ! -f ../wal_archive/%f && cp %p ../wal_archive/%f