Add button to assign factions and locations in lobby

[bill-rich]

Instead of having to go in-and-out to get factions and locations, add a "RANDOM" button to assign them in the lobby. When playing online, having to go in-and-out is difficult if you're trying to get the same players back into the lobby. Even for groups in private lobbies, this saves considerable time and frustration.

Demo video: https://youtu.be/NXqxbTme6eg
Branch with working code: https://github.com/bill-rich/GeneralsGameCode/tree/random_button

In the branch where I've implemented the feature, I've copied the in-game logic for assigning both location and factions.