Development towards 0.8

* Automatically fill the SORTODER metadata, according to the OS and the version of the OS. This is used by cyclades to order the available images.
* Automatically fill the GUI and the KERNEL metadata. This can be used to display information about the image in cyclades.
* Disable Windows Update before booting the Windows VM, to install the VirtIO metadata or to perform syspreps. This makes the Windows preparation process less fragile.
* Support locally mounting the image to the host system either to run a script on it or manually add, remove or alter files.
* Add a sensitive_userdata sysprep parameter. This way the user may change the files that will be removed from the media's home directories.