Basic title screen support

Changed the title screen GUI script to place buttons based on Transforms
in the world. It's better documented in Assets\Scripts\MainMenu.cs
Currently the buttons are haphazardly scattered about and don't have
custom sprites, but I wanted to at least push the proof of concept
before I went home for the night and couldn't work.
From left to right, the buttons are Level 1, Level 2, Quit.

When I get back to work on this, I intend to make actual mock-up sprites
for the buttons, put them in reasonable places, and remove the text from
the background itself (just to prevent possible issues later.)

I hope I'm committing correctly.