Move all config to `/config` JSON files

[mmathieum]

Let's try to move all configurations values to 1 directory JSON files and everything else should be generated files.

• /config
  • gtfs
    • feed.json
    • agency.json
    • route.json
    • direction.json
    • trip.json
    • stop.json
    • ...
  • gtfs-rt
    • feeds.json
  • gbfs
    • ...
  • news
    • youtube.json
    • ...

Could also automate XML -> JSON migration when possible?
Once file migrated, old file should be git rm.