Standardize DB Params on OptaPlanner Employee Rostering template

To set up a XA Datasource in OptaPlanner Employee Rostering template we had to tweak the env vars a little bit:
https://github.com/jboss-container-images/rhdm-7-openshift-image/pull/263/files

Those vars are the ones looked up for the EAP Datasource Module. In the ideal world, we have a standard across the templates to configure datasources. It's needed to revert back to these vars:

RHDM_DATABASE
RHDM_SERVICE_HOST
RHDM_SERVICE_PORT

This can be done with a new function on the optaplanner module scripts. We can either export the vars expected by the EAP Module or create a new URL var, depending on RHDM_NONXA variable value.