Allow the player(s) to have multiple save files

[gehrigweber]

Right now, games are saved to one and only one file. Games can only be loaded from this file. Make it so that, when saving a game, the player can choose a name for their saved game file. When they load a game, make it so that the player can choose which file to load.

(Estimated 100 points)

[brianslee]

W18 ok. 150 pts