Renamed "FootStepMostImportantEventProcessor" to "FootStepMostImportantStimulusProcessor" and extended JSON transformation

Also, moved two long-running scenarios to "Scenarios/Demos" to shorten
the integration test phase of Vadere.

Also renamed state package "psychology.stimuli" to "psychology.perception".

Also renamed following classes:
- "EventCognition" to "StimulusProcessor"
- "SalientBehaviorCognition" to "SalientBehaviorProcessor"
- "EventController" to "StimulusController"

Watch out: Event output processors and also the existing scenario files
have not been migrated. Therefore, the unit tests fail at the moment!

Also, deleted dummy test files for renaming "event/events" to "stimulus/stimuli".

Two aspects are missing so far:
- Writing a migration to rename nodes in JSON representation.
- Rename controller classes and unit tests.

In "run_vadere_console_with_all_scenario_files.py", use "os.path.join()" instead of hard-coded platform-specific path separator

In ".gitlab-ci.yml", deleted outdated comments and made stages "unit_test" and "integration_test" more robust

VadereGui/src/org/vadere/gui/onlinevisualization/view/OnlineVisualisationWindow.java:
- Fixed bug: The scroll pane was not added to the underlying model.
  Therefore, it was not possible to capture mouse wheel events.

add tests to solve the eikonal equation on the unstructured mesh for 2 scenarios (bridge and filled chicken).

Added "AbsorbingArea" and "TargetChanger" to "TopographyIterator" to make them selectable in PostVis

In "TargetChangerController", added optimization to avoid unnecessary calculations of dynamic floor fields

In top-level "pom.xml", use new versions for "commons-configuration2" and "commons-beanutils" to avoid logging a stack trace