This PR adds a self-contained demo test and thereby resolves #195. As stated in the javadoc:

/**
 * This class serves as self-contained analysis demonstration using the simple PCM and DFD instances of the online shop.
 * The two initialize methods showcase the analysis setup for PCM and DFD, while the test methods show how to analyze
 * both PCM and DFD models with and without using the ConstraintDSL, and also how to use the QueryDSL. The high degree
 * of code duplication within the tests (e.g., in manual querying) is intended for the sake of self-contained tests.
 */

Open tasks:

• Play with different models / constraints to produce violations that can be easily understood
• Fix formatting
• Discuss whether the test is appropriate and whether anything is missing
• Add DFD tests
• Add QueryDSL demonstration
• Discuss whether the "duplicate" results of the QueryDSL demonstration (which are not duplicates but contained in multiple TFGs) help or hinder the learning process (filtering them out would blow up the "minimal" demo code and hide the nature of "duplicate" items)