Add worst offenders page

[ceddlyburge]

In much the same way as #28, it would be good to show a list of the players with the most penalty cards.

This should happen after #38, which will invovle parsing the card details from the api response and updating the model with new types to represent the cards.

Different sports have different meaning for their cards, and different colours, so the code can't really know the relative importance of each, so instead it should use a heuristic. The cards that appear most rarely in the spreadsheet will be assumed to be the worst, and be given higher rankings tha those that appear more commonly.

The players will be ordered according to this ranking primarily, and then by player name and team name.

The cards should be displayed using their icons as in #38, along with the number of them that the player received.