Document the API data models and schema

[jtanzi]

Document the data models (categories and properties) for all data models that will be handled by the Streetlights API. Also, all methods that the API will support for clients (front-end application) requesting data.

e.g.

Streetlight: {
id: string,
bulbType: 'Inc' | 'LED' | 'Fireflies',
wireless: boolean,
fixture_mfg: string
}

Methods:
getStreetlight(id):
Returns a single streetlight.
Parameters:
id: the ID of the streetlight to be returned.
Returns: JSON