Score & Combo

[mikewesthad]

• [x] Show score as 0000010 (with leading zeros grayed out)
• [x] Move score to right side of the screen and place combo indicator below score
• [x] Display combo as 1x, combo starts at 1
• [x] Hide combo when no combo is active (e.g. combo <= 1)
• [x] Each kill adds 0.1 to combo
• [x] 2 seconds without a kill ends the combo
• [x] Getting hit ends the combo
• [x] Combo and enemies killed are tracked, and the final score value is applied when the combo is ended.