Chem grenades asay logs improvements

Makes fingerprintslast use ckey instead of key
Cleans a bit the prime() code, large grenades won't be a huge copypaste anymore
Asay logs will now show up when the grenade is activated instead of used. Only when The grenade is activated by an assembly.
New proc, get_mob_by_ckey(). Give it a ckey and it will return a mob.