Fixed bug: Medkit not disappear after used

Added Armor, marine who equips this can still survive after being hit (will take 2 hits from drones before dying from full health)

Added mining laser to burn/destroy biomass (get this if you need to burn some biomass)

Balance Update:
All marine have same walking speed and health.

Marine can only carry max of 2 hand grenades as their offhand items, it can be refilled by taking from ammo stash (it will never disappear even if it's 0), grenades can still be used to burn biomass, but it's better to let someone bring mining laser to conserve your grenades.

Rifle's damage is slightly reduced to maintain the balance of the game

Drone's fire resistant is improved, flamer is no longer effective to kill them (if you managed to get flamer on certain maps)