Pull GBFS system_id from feeds in stead of systems.csv

[mplsmitch]

The GBFSsystem_id field is a globally unique ID used to identify each shared mobility system. It's supposed to remain unchanged for the life of the system but in practice they do sometimes change. These changes are not reflected in the Mobility Database because they're being pulled from systems.csv.

We should be pulling them from the system_information.json file so that any changes would be reflected in the Mobility Database.