Migrate the demo app to managed configuration 🎉

[zionts]

Migrate the federation-demo to run using managed federation.

TODO

• [ ] Migrate the instructions from the commits into the README
• [ ] Allow the gateway to run with a serviceList as well, with a task to pair
• [ ] Set up convenience npm scripts to publish services

[Enalmada]

This is interesting. Think at the very least there should be a note about the option in the readme

[tizmagik]

+1 @Enalmada -- I think for the purposes of this demo, the serviceList approach is very illustrative