Use Cloud Endpoints and OpenAPI

[Splaktar]

More details on Cloud Endpoints: https://www.youtube.com/watch?v=bR9hEyZ9774&list=PLIivdWyY5sqJg2FeM9_NPBL07BxATY06I&index=9

This would allow us to auto generate the API docs page and supports enforcing quotas, applying API keys, or requiring Firebase Auth for API usage. It also would give us metrics on which APIs are the most active.

[Splaktar]

We have one endpoint working so far from this branch:
https://20170318t053637-dot-gdgx-cloud.appspot.com/api/v1/chapters

The rest of the OpenAPI spec for the API needs to be written before the other APIs will work.

That linked instance is also connected to a new MongoDB instance in the default network instead of the gdg-x network. We need to retire the gdg-x network and everything on it because the old Legacy networks are more or less not supported now.