Balance tweaks + one bugfix

-Fixed a bug which had a chance of causing a missing boss in endless mode
-Stuns from lightning/plasma weapons last a little longer
-Fire damage over time is a little stronger
-Radioactive projectile weapon ammo does a bit less damage
-Dreadnought turrets have less health
-Disintegrator beam is a little longer
-Photon rounds are now much more accurate and have very strong knockback
-Shockwave sprite on explosions is a bit bigger
-Safety ammo now has more splash radius
-Nuclear missiles can now use safety ammo, have fun nuking yourself!