Instead of letting the 'engine' module create two artifacts - the main Validator jar, as well as the 'testing' jar (using a qualifier), the testing code should be moved into its own module.

This servers two purposes:

1. Stick to the Maven rule - one module one artifact
2. Works around some issues in Intellij where module dependencies are not set-up correctly in case a module depends on two artifacts (the main one as well as one created with a qualifier) of another module.