simple score-system, more ammo-types

introducing a simple scoring system, where each enemy stores a
point-value that is added to the score when he was killed.
the displayed score has leading 0-digits!!!1!!1!
scoreText, nmbrOfScoreDigits should be moved into a seperate class "hud"
later on..

defined several ammo types for the player. they dont have a unique
sprite yet and aren't selectable.

also added the color-pallette-graphic for MyColors