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
This makes some tweaks to the engine to support this, specifically, it tweaks the hardcoded shaderpaths to defer to a pref variable, so none of the shader paths are hardcoded.
Also tweaks how post effects read in texture files, removing a bizzare filepath interpretation choice, where if the file path didn't start with "/" it forcefully appended the script's file path. This made it impossible to have images not in the same dir as the script file defining the post effect.
This was changed and the existing template's post effects tweaked for now to just add "./" to those few paths impacted, as well as the perf vars to support the non-hardcoded shader paths in the engine.
