Support setOrder() for TraCI connection

[sk13]

This modifications allow to set the client id while connecting to Sumo, which in turn allows Artery to be one of multiple clients connected to the same sumo instance (e.g. to allow co-simulation of Artery and Caral using Sumo).

[riebl]

Thanks @sk13! I have merged your commit as df62beeed519caa44b4573dfd269ff40e64c1fca with some minor changes:

• renamed clientID to clientId
• fixed some whitespace issues