Remove ammo from consumed tools/gun when crafting

As described here:
https://github.com/CleverRaven/Cataclysm-DDA/pull/6234#issuecomment-35764136

If the crafting consumes tools/guns that are loaded, it will consume the loaded ammo with it. This does not happen when one disassembles an item. In that case the loaded ammo is dropped.

I moved that code out into its own function and called that function from `game::complete_craft`. Items used for crafting will be unloaded (if possible) before used in crafting.