Wear bedsheets... on your back!

This will let you wear any bedsheet on the back slot, so now anyone can wear a cape if they so desire (and don't mind losing their backpack).  Capes do not do anything and have no practical benefit.

Changes:
* Added loads of sprites for wearing capes on your back.  Each color has it's own sprite.
* The Head's bedsheets now have an 'emblem' (think of the Captain's Nanotrasen symbol) on their bedsheet that resembles their department as well as two gold stripes.
* Quartermaster has his own bedsheet, which can be made with his stamp.  It has a silver emblem and one silver stripe.
* The CMO is finally a true Head of Staff as his stamp now makes a unique bedsheet, complete with gold stripes and emblem.
* Changed the bedsheet sprites on the ground to reflect emblem changes.
* A few extra bedsheet/capes were added.  Centcomm, syndie, cult, and wizard bedsheets can be spawned by admins for gimmicks/events.  They're very stylized and resemble actual capes instead of just bedsheets tied around your neck.
* Most bedsheets have a unique description (which sadly get overwritten when you wash one.)

Pictures:
* Most of the capes, note that head capes are out of date here: http://i.imgur.com/bkcNTQW.png
* Centcom and head capes.  CMO cape outdated: http://i.imgur.com/2IeiO7i.png
* Special admin capes, CMO, and QM capes up to date: http://i.imgur.com/Nfq2FtF.png

Since you lose your back slot and wearing a cape looks rather silly, this is meant to be more of a gimmicky thing but it has potental for a lot of admin events and such.