add quickie gui library as git submodule
add title screen menu

use quickie. title at top of screen, menu containing items to play
game and to quit. uses default quickie theme which doesn't look good
for this game, so that needs changed.

replaces previous text being drawn for the title and "press enter"
use quickie for game over screen
use quickie for survival mode gui
initialise global gui settings in main
use custom gui style for buttons and labels

labels simply draw their text in white. buttons draw their text in
white when in normal state, and gold when active. no background for
buttons, just text.
use 800x480 resolution
make human always run, use control key to strafe