Tunes player hitvelocities, polishes gold pickup, fixes garish colorclashing in the environment, adds slayslime

hitvelocities now fall off for number of enemies hit, can be varied
between X/Y. Knight's firstswing knocks back and up, secondswing knocks
back and down.

Added 'KillParent' to ControllerEvents.

The foreground just wasn't affected by the ambient light color which is
why it looked too bright and clashed with the background. That's also
fixed, at least temporarily. Ideally the players etc should also be
slightly affected by ambience, but not as much so they still stick out.