GameSetup GUI cleanup - Renaming.
- rename 'Controls' class to 'Controllers' to avoid ambiguity and mimic MVC lingo.
- rename GameRegisterStanza into LobbyGameRegistration, and make it explicitly a controller.
- rename GameSettingsFile to PersistentMatchSettings & move it to its own folder (since it could be reused independently of the controllers)
- remove the StartGameController & move launchGame to the GameSettingsController (simplifies the control flow)
- the GUI Object "setupWindow" was actually the GameSettingsPage, this is corrected.
- the LoadingPage was showing the GameSettingsPage -> in the current code, it makes more sense to have both handle their own visibility.
- make the NetMessages class independent of other gamesetup logic, so that it can be reused by other code. Remove the custom XML object.
Differential Revision: https://code.wildfiregames.com/D3719