Docker-based test projects

[dodie]

Currently, Scott has two test suites:

• A "baseline version" on Java 8 and JUnit4, containing the majority of the tests.
• A "cutting edge version" on the latest Java and JUnit 5, containing the tests that are related to the new Java or JUnit version.

This imposes some limitations on the project's development and test coverage:

• it's not practical to test various combinations of libraries or other JVM versions
• the majority of the tests are defined in the "baseline" test group, which is never ran on the latest Java versions
• one always has to have the latest Java installed to build the whole projects, however, the core part could be built with any Java version

As a possible solution, the project could also use containers to run the test, where it would be easier to define any kind of Java dependency. Also, in the future, it would enable to test integration with various build tools more easily.

[dodie]

The Azure Pipeline is aligned to run the test suite in a docker container, and the development guide is updated to contain instructions on how to use the project with docker.