Title screen animation

Animation is controlled by animator controller, not through code. I
commented out all lines that affected the animation in code. If the
game has started, the "Quick" sprite's sprite renderer is disabled.
Added a_enemy1 sprite sheet. (Fully sliced)
Made new A_enemy damage and death sprite sheets. (Sliced)
cleanup
letter crumble and destroying complete

for letter A
Added SoundSystem and music track.
falling letters and losing implemented
tightened
Merge branch 'fallingLetters_fromTitleAnimation'