Adding synchronous API request for the videoroom plugin

Added a API request handler that will return a list of the current videorooms. Also, added a todo, to determine if we want to list participant details in this request or add a new room details request that will do that(if that is something desired).

Added a API request handler that will tell if a room exists or not(does not list any details). This is for a quick and small check against the gateway for room existence so that the client API caller does not have to worry about error handling(say, when trying to create a room or add itself to a room).