Doc: Minor improvements to template content in Deploying guide

Based on a discussion regarding the future of templates for Broker install/deploy, I suggest the following minor changes in the Deploying AMQ Broker guide: (https://access.redhat.com/documentation/en-us/red_hat_amq/7.7/html-single/deploying_amq_broker_on_openshift/index#deploying_broker-on-ocp-using-templates_broker-ocp)

• add a note, or a sentence in the existing intro para (4.1), to advise customers to use the operator instead of templates for new deployments
• possibly link from Chapter 4 back to Chapter 3, Comparison of deployment methods, to make sure the customer has considered that info before deciding to use a template
• in the comparison section of Chapter 3, move the operator method to the top of the section