Endpoint to dump all known entities

[colacadstink]

Dialogflow requires a list of "entities" (the variables in a request - "park hours for $park", "wait time for $ride", etc.) to be maintained internally, which needs the entity name, and a list of synonyms for that entity (so stuff like "the epcot ball" maps to "ep.spaceshipEarth").

It'd be incredibly helpful if there was a page/endpoint where you could GET the list of entities the API is currently aware of. This would make it easier to ensure that Dialogflow and the API stay in sync with what entities exist and what they're named.