Moved the SoundManager and the 2D math function (helpers) from the shooter demo to the fife extensions. Fixed fife_timer as it didn't work in the first place. Modified the SoundManager to use the now working fife_timer and removed the Timer class from the shooter demo entirely

<HBox opaque='1'>
	<Label name="Title" text="Rio de hola - FIFE 0.3.1"/>
	<Button name="quitButton" text="Quit"/>
	<Button name="aboutButton" text="About"/>
	<Button name="optionsButton" text="Options"/>
</HBox>