Finish Laser Gun Fuck

Laser Gun is a fucking-time-consuming job for an idiot

Function:
A beam follows the nearest enemy and changes targets when needed.
You can set the following parameters of the gun(and beam):
- float AttackPeriod: an attack per period in seconds, default : 1 sec
- float[] attackDamageList: the damage every attack makes
- float[] damageIncreaseRateList: increasing ammount of attackDamage

others paras are inherited from Weapon