Add listener to GameEnd event, tracking stats

[FubyCutie]

create a stats data class which will hold various details about a player which will be updated based on the data from a GameEnd event, each game will likely implement it's own gameEnd event, which will extend this main one, so they can include more details as needed

[FubyCutie]

somewhat done in c783cec

[FubyCutie]

What format should the stats be in, a Comparable? This would allow for the most freedom