Implement replicaLoadBalancer boolean flag. (#38)

The flag adds a replica service with the name cluster_name-repl and
a DNS name that defaults to {cluster}-repl.{team}.{hostedzone}.

The implementation converted Service field of the cluster into a map
with one or two elements and deals with the cases when the new flag
is changed on a running cluster
(the update and the sync should create or delete the replica service).
In order to pick up master and replica service and master endpoint
when listing cluster resources.

* Update the spec when updating the cluster.

pkg/util/users/users.go

@@ -18,9 +18,14 @@ const (
 	inRoleTemplate   = `IN ROLE %s`
 )
 
+// DefaultUserSyncStrategy implements a user sync strategy that merges already existing database users
+// with those defined in the manifest, altering existing users when necessary. It will never strips
+// an existing roles of another role membership, nor it removes the already assigned flag
+// (except for the NOLOGIN). TODO: process other NOflags, i.e. NOSUPERUSER correctly.
 type DefaultUserSyncStrategy struct {
 }
 
+// ProduceSyncRequests figures out the types of changes that need to happen with the given users.
 func (s DefaultUserSyncStrategy) ProduceSyncRequests(dbUsers spec.PgUserMap,
 	newUsers spec.PgUserMap) (reqs []spec.PgSyncUserRequest) {
 
@@ -55,6 +60,7 @@ func (s DefaultUserSyncStrategy) ProduceSyncRequests(dbUsers spec.PgUserMap,
 	return
 }
 
+// ExecuteSyncRequests makes actual database changes from the requests passed in its arguments.
 func (s DefaultUserSyncStrategy) ExecuteSyncRequests(reqs []spec.PgSyncUserRequest, db *sql.DB) error {
 	for _, r := range reqs {
 		switch r.Kind {