List all Leaderboards in an organization. Each Leaderboard object contains details on created, updated, start, and end dates, the identifier, status, ID of group by Attribute, flag for allow Group Detail, display style (competitive or relative), maximum number of records/standings to display, display attribute settings, isAnonymous flag to display user as Anonymous on the Leaderboard, isSecret flag to not display that Leaderboard to the users and the leaderboard image ID. Leaderboards should be enabled for the organization using Update Organization API in order to access collections, leaderboards and leaderboard contests.