NSIS fixes #385, #831

 1. NSIS HKEY_CLASSES_ROOT Registry Cleanup (leftover app keys)
 ![image](https://cloud.githubusercontent.com/assets/6345473/3254073/74fb4bea-f1eb-11e3-9eb2-99eafb806e01.png)


 1. NSIS Branding Fix, Change to 256 color bitmap, `nsis_branding.bmp` now displays properly
![image](https://cloud.githubusercontent.com/assets/6345473/3254558/9c6a5ab8-f1fa-11e3-8a6d-d5496a10efe6.png)