Have initServer only get called when a server is actually started for the first time
Added utility method callGamemodeFunction to streamline exec'ing of gamemode function calls
Added onClientConnect gamemode function, called when the client establishes the connection
Added onInitialControlSet gamemode function, called when the client actively gains control in the game, to allow gamemodes to special override GUI settings or input commands
Cleaned up init'ng of the engine so stock UI module isn't required to trip configuration of the canvas
Added fallback so if nothing set the main content control for the UI after boot, we attempt to set the defined mainMenuGUI, on the chance nothing explicitly sets it on load
