Start Menu+, Menu Navigation and Loading Screen

I lied - the game still doesn't work. An anomalous memory management
issue is blocking functionality past the loading screen. However, much
has been changed, improved and polished, so that's nice.

- Start Menu fully functioning.
-Menu navigation, (ie "Options" opens the options menu) and predecessor
navigation (ESC goes "back" to the previous menu) functional.
-Converted print loading messages to GUI Loading Screen