weapon code cleanup

removed laser damage tuning
added explosion values in content.py
made explosion force independent from damage
removed unused nodamage parameter in CreateExplosion
took projectile damage for explosion maxdamage
linked all weapon damage values to content.py
linked all weapon max ammo values to content.py
improved variable usage in CPickup::Tick()
replaced some 0s by false as it should be
stopped regenerating  infinite ammo
removed m_Ammocost in CCharacter