Fix postgis

Use better, more puppetlabs-postgresql way to work with the postgres module by using postgresql::globals. This change takes us closer to be able to propose the change to upstream maintainer. I was not comfortable proposing early version. One problem is that we still need Modulefile due to outdated puppet version. World uses >= 3.6 these days and Modulefile is obsolete starting version 3.6.

Proposed upstream pull https://github.com/camptocamp/puppet-postgis/pull/31