Add support for new fields in external services template

In some cases, it might be useful to be able to edit the externalTrafficPolicy and loadBalancerSourceRanges options of the load balancer or node port services. Their value might be in:

• Propagating the real source IP address into the Kafka brokers (externalTrafficPolicy)
• Making sure the routing is more efficient by not routing node port traffic between nodes not hosting the endpoint locally (externalTrafficPolicy)
• Configure the cloud provider firewalls to allow connections only from some IPs (loadBalancerSourceRanges)