Various small fixes

Getting kills in PvP now displays a message (can be disabled in options) Pushing asteroids into players now gives credit Asteroids no longer break in multiplayer Background fade can now be toggled in graphics options Powerups now have a cap but do not timeout Powerups are now synced in multiplayer Bosses have more HP Improved bot AI Penetration stat on energy beam + gatling beam Irradiated enemies now glow Buffed disintegrator Renamed aim to 'Sniper Camera' in controls