Refactor test classes

[GLaDAP]

Currently there are a lot of integration tests in the driver, but the parts tested are not clear and the expected results are not always evident from the test title and assertion. Documenting the test classes can improve debugging, especially test classes with very similar titles

• Document test classes
• Separate integration and end-to-end tests away from unit tests
• Mock functions where required with e.g. Mockito
• Where possible make tests smaller
• Split tests in separate classes based on what functionality is tested so tests can be executed in parallel in CircleCI
• Use CircleCI workspaces to prevent double build of driver jar
• Upgrade to junit5
• Use parallel execution of tests to decrease build time

[GLaDAP]

Properties file for parallel test execution added in #193, together with separate build and test steps in CI, where the tests are ran in parallel where possible. Some tests which where previously executed in a for-loop now use JUnit ParameterizedTest annotation, which enables checking individual test cases