Populate csv files within a folder to populate a sport with players, part 1

@ShaiNirShado 

This one gets the most basic functionality that we're looking for. It goes through all csv files in a folder at the root called ```default_players```, then it'll go through the columns as necessary and add them to the database, and add them to the proper sport id. (Format for CSV files are written in the comments).

Next up on the list is to manipulate strings in the csv so this process isn't so troublesome where we have to manually edit all the csvs to this format, and to label rookies. 

As for the other PR, can probably safely close that one (it's mainly for review purposes), but I was wondering if we should just run this populate method when we create the new sport?
Can you add some automated testing to make sure this generates player models correctly? You can test a few players with an abridged CSV.