Integrate Geoscenario Server pedestrians into Ring Road map

[scott-larter]

The purpose of this PR is to integrate GSS pedestrians into the ring road map.

Summary of changes:

• New osm map file: lanelet2_ringroad_pedestrians.osm
• New pedestrian scenario using ringroad map file: gs_ringroad_single_pedestrian.osm
• Minor code changes to path planning method in sp/SPPlanner.py to accommodate ring road crosswalk structure

To test, run gs_ringroad_single_pedestrian scenario with various configurations (number of pedestrians, starting positions, goals, etc.)