fix wrong polygon intersection computation, add an additional PedestrianFundamentalDiagramProcessor.

quick fix in PedestrianVelocityProcessor: the velocity was NaN if the duration was 0.0 now the velocity will be 0.0

Dev/step size adjuster

See merge request !36

Measurement areas are not defined yet.
Free-flow velocity is not yet adjusted.

Added script "osm2vadere.py" to "Tools" folder, to convert OpenStreetMap maps to a Vadere topography.

CHANGELOG.md:
- Added the section "# Changelog: Vadere" and corrected indention level of following sections.
- Also adapted the correspoding guide "Writing Changelog Entries.md".

Reactive useFreeSpaceOnly=True again, closes #109

Closes #109

See merge request !35