New jackboot sprites, combat boots, and workboots

- Added work boots for engineers to replace their orange shoes (which are really for prisoners, as a bright-orange badge of shame.)

![afdfd](https://cloud.githubusercontent.com/assets/7247232/5544259/ca2ff7cc-8ab7-11e4-8da9-dd55fcd5dd86.png)
![ss 2014-12-23 at 03 20 01](https://cloud.githubusercontent.com/assets/7247232/5544256/b9fe8d32-8ab7-11e4-8ffd-3d0278cc71d8.png)

- Changes jackboot sprites and gives a unique sprite to combat/swat boots (nuke ops get combat boots, death squads get swat boots)

OLD
![ss 2014-12-23 at 02 25 34](https://cloud.githubusercontent.com/assets/7247232/5544263/e2858698-8ab7-11e4-99d2-5cdcaf02e88f.png)

NEW JACKBOOTS
![ss 2014-12-23 at 03 19 48](https://cloud.githubusercontent.com/assets/7247232/5544264/e62065e8-8ab7-11e4-8cd2-912b10089623.png)

NEW COMBAT BOOTS
![ss 2014-12-23 at 03 19 57](https://cloud.githubusercontent.com/assets/7247232/5544265/ecdbdc5a-8ab7-11e4-9329-6aa430aa5a40.jpg)