Numerical Ids (Part 1).

Due to the ever changing nature of our id system, we are now introducing numerical ids as another option on all of our sports/leagues/teams/players/fixtures/tournaments models.

Currently, the first step is just exposing these, the next part will be allowing users to make requests using them.

In addition, we have gotten some requests from users about wanting a way to know whether the player is the same across leagues. Currently, Lionel Messi has a different ID per league, we are also introducing a base_id on the Team and Player model that can be used to identify that the player is the same across leagues. Request support will be coming in the future.