* Unify templated files

A lot of files are identical throughout the different packages.
This is the base for unifying them for easier handling.

* Feature: Add PHPUnit compatibility layer

Derive your tests from \Joomla\Test\TestCase instead of \PHPUnit\Framework\TestCase to avoid problems with the signature change in PHPUnit 7.0.

* Deps: Don't require DBUnit

It is suggested, no (test) code is relying on it being present.