Bugfix/git shortcuts

Hello,

After installing Git with Chocolatey, I was quite disturbed by the fact that its various shortcuts were not installed by default. As I believe that such a behavior is not an acceptable default setting for the masses, here is my pull request containing the related changes.
@ferventcoder Oops, I did not see this issue. Sorry for this.

As seen [here](https://github.com/msysgit/msysgit/blob/master/share/WinGit/install.iss#L301-L334), this issue only occurs when chosing to use the cheetah plugin. It is a Windows Explorer DLL required to offer more appropriate menu items depending on the selected file(s) or directory(ies).

Would simply installing the registry-key shortcuts (i.e. not loading any additional DLL in explorer.exe) be OK for you?