Adds improvised shotguns and fixes paths for wrap paper

Wrapping paper was /obj/item/weapon/wrapping_paper, as well as packageWrap. These are both 'pseudo stacks' so I converted them to actual stacks, in the /obj/item/stacks/wrapping_paper path. This means a lot of path changes in the maps. They still function fine as actual wrapping paper and stuff but now they can be used in construction, like...

*Improvised shotguns!*
![ss 2014-10-16 at 10 55 50](https://cloud.githubusercontent.com/assets/7247232/4667497/a50fe388-555d-11e4-9060-6c6cc7215d20.png)


One shot break-action improvised shotguns made from either table construction or more traditional methods (this part can be removed if the code for it is too bloated).

Sling optional, but you can't carry it on your back without it! The sling is made from 10 lengths of cable coil and simply attached to the shotgun.
I really hope this isn't copypasta'd from the other shotgun sawoff proc. You should know better by now.