Feature - PHPUnit hardening

This PR is a **work in progress**.
I wanted to make a quick PR without setting up all of the required DB's for the full test suite...

Anyway, this PR simply sets more strict defaults to the `phpunit.xml` file to make PR merging more safe. I've also renamed the `phpunit.xml` file to `phpunit.xml.dist` since its a default distributed configuration (that's the new standard practice).

:+1: