v0.5.3: Ship- and Weapon-Specific Items

System Changes

1. I now have the ability to mark certain Items as excluded from certain Ships and Weapons, similar to Upgrades.
2. I can now also grant Ships and Weapons their own unique Items that don't apply to others.

Item Changes

1. The Engineer can no longer get the Extra Projectile item. I am glad Kyle had a lot of fun with the old implementation but it was way, way, way too strong. What was I thinking!!
2. The Sword weapon is similarly no longer offered the Extra Projectile Item, since it didn't do anything. (You did not get a second sword.) I am open to arguments about this if you think it could be cool to dual- or triple-wield swords.
3. The Sword weapon is no longer offered the Piercing Item, since the Sword cleaves enemies by default anyway.
4. The Rail Gun is no longer offered the Piercing Item, since the Rail Gun projectiles pierce everything anyway.
5. The Engineer has three new items, corresponding to each of the three Drone types. The Items add the Drone in question. So now you always get to pick a Drone after the round is over, but you can also roll into another Drone when you level up.
6. The Sword has two new items:
   1. When you reflect a bullet with your sword, the bullet's damage is doubled. This can stack really high really quickly (4 of them is a x16 multiplier, for example).
   2. When you reflect a bullet with your sword, you heal 1 HP.

Gameplay Changes

1. Before, all projectiles that were deflected by any means had their damage multiplied by 10. This is no longer the case. If you want to kill a lot of enemies by hitting their own bullets back at them, you need to play Sword and take that Item.

Coming Up

1. I'd like the Sword to get another Item to make it longer. I tried this but I had a lot of problems with scaling the collision shape alongside. I will likely have to split the Sword sprite into two pieces -- handle and blade -- and then only scale up the blade portion.
2. Engineer can get an item that reduces all Drone cooldowns by, I don't know, 10%.
3. I would like to have the Engineer's drones proc more smoothly instead of the current bursting behavior.