Adds MOLLE pack.

Noncraftable, rare military backpack that statistically fits between
backpack and rucksack.
Tweak.
Adds 2.5L (10 volume) plastic canteen.
Minor formatting cleanup.
Adds atomic energy drink.

Utilizes new ATOMIC_CAFF iuse function.
Merge MOLLE pack, Atomic Energy Drink, 2.5L canteen, melee.json tidy.