updates and enhancements

* Modified the gemfire_store to gemfire_module
* Modified the gemfire service to "pivotal-gemfire"
* Changed service's locator to host

All changes are tested with the latest GemFire service broker and GemFire BOSH Release:
https://github.com/jcherng-pivotal/cloudfoundry-brokers
https://github.com/jcherng-pivotal/gemfire-bosh-release