Without this line, the empty attribute object will be removed.

ids in rimea_04***h.scenario

* remove duplicated 'move' call in osm sequential update schema.
* add 'dirtyFlag' to topography LinkedCellGrid for pedestrians and
  cars. For instance the BHM model does not update the LinkedCellGrid
  in one simulation step.

Improve stair tests and one test passes now in CI.  

See merge request !37

In "serializeEvents()" of class "StateJsonConverter.java", use "prettyWriter()" instead of "writeValueAsString()" to get a nicely formatted output under "Event" tab.

* add new fields to AttributeOSM
* correct typo in PedestrianDensityGaussianProcessor

# Conflicts:
#	VadereSimulator/src/org/vadere/simulator/models/osm/updateScheme/UpdateSchemeEventDriven.java

# Conflicts:
#	.gitlab-ci.yml
#	VadereGui/src/org/vadere/gui/projectview/view/ScenarioPanel.java
#	VadereSimulator/src/org/vadere/simulator/models/bhm/PedestrianBHM.java
#	VadereSimulator/src/org/vadere/simulator/models/osm/updateScheme/UpdateSchemeEventDriven.java
#	VadereSimulator/src/org/vadere/simulator/models/osm/updateScheme/UpdateSchemeSequential.java
#	VadereState/src/org/vadere/state/scenario/Pedestrian.java
#	VadereState/src/org/vadere/state/util/StateJsonConverter.java

Refactored "osm2vadere.py" and added unit test "test_osm2vadere.py" (written by Maximilian Niedermaier).

fix a problem with the AreaSoeedProcessorTest and PedestrianVelocityProcessorTest: Wrong expected values.

# Conflicts:
#	.gitignore

Bugfix in "Simulation.java": "cognitionLayer.prioritizeEventsForPedestrians()" must be called after "sourceController.udpate()" and "topographyController.update()".