Use libsumo instead of TraCI socket integration

With recent SUMO versions one can use a direct C++ library "libsumo" as TraCI API instead of the classic TCP based client/server architecture to provide access to SUMO. This might be a performance and stability improvement for future integration.

Advantages

• Faster with high number of vehicles
• Less error prone integration
• No need to adjust and check TraCI interfaces with new SUMO versions

Drawbacks (as of 21.10.2019)

• Not running with SUMO-GUI (!) -> blocker right now
• Subscriptions that require additional arguments (vehicle.getLeader) don't work -> we may not need this now

Further reading

• https://sumo.dlr.de/docs/Libsumo.html
• https://sumo.dlr.de/docs/TraCI.html