Moved the file cleanup to a CleanWindows function which simply deletes
all the files a Windows compilation generates for the icon resources.
Windows resource files MUST be in the same directory as the `go` source or
it will not be included in the resulting binary.
package.PackageWindows should be renamed to `GenerateWindowsResources`
since it doesn't actually package anything but rather generates the
various resources that are used during compilation.
75be8f698a