Began Sprint2 Demo

* Modified AltMenuScreen and ButtonPanel to take three Runnables instead
of one, to launch single and host/join multiplayer games.
* Changed up some variable names and wording to make 'hosting' more
clear
* Modified UI Test Application to use multiple buttons, which currently
do nothing (for that test only)
* Created sprint 2 demo runner, and 3 apps which launch different game
behavior (single player, hosting, and joining multiplayer)