Weaponising chemistry for overmap combat

[Cyaneer]

Make medical be able to print plastic propellant bags that use reagent explosive power for powder strength.

It would be very good for the medical game, as chemistry will now have a good way to actively involve itself in overmap combat besides manning gauss/50cal or waiting for SS crit to cut the ship in half.

Also would give admins much joy in the way of "watch chemistry mishandle dangerous amounts of explosives", with all the funny that implies.