[RFE] Introduce standalone version of makeupdates

[msekletar]

As a package maintainer I'd like to have a simple tool which I could point to set of rpms or a directory tree and it would produce the very minimal updates image that contains exactly the content of rpms or directory tree.

The current model where I need to download the entire Anaconda source tree, checkout the correct branch that matches the installer image I want to patch is mostly suited for anaconda developers.