Bump version to 0.7.4
Rename **kargs to **kwargs

This complies better with the python conventions
Miror fixes in comments
Use the device mapper to snapshot raw images

Do not use qcow2 to snapshot images that are raw. qemu-nbd is not
present in some old systems like CentOS 6.x. All we can do to support
those systems is to use the device mapper in as many cases as possible.
Handle the case where qemu-nbd is missing

If qemu-nbd is not present at the host system, only accept raw images
as input media. This is a workaround for ancient systems like CentOS 6.x
where the nbd module is not compiled in the default kernel and the qemu
package does not include the qemu-nbd executable.
Update ChangeLog and version.py for 0.7.4
Merge branch 'hotfix-0.7.4'
Merge branch 'master' into develop

Bump version to 0.7.4next
Create tmp file to display a fatal error in dialog

When working with the dialog-based version of the program and a fatal
error occurs, create a temporary log file and put the full output of the
program there. This makes it easier for the user to determine what went
wrong.
Assign a SORTORDER metadata to the image

This is automatically assigned according to the OS type and the
distribution of the image.

This resolves #9
Detect the installed kernels on Linux systems

Fill the KERNEL image property with the version of the latest installed
kernel found in the input media.
Change an output message to success
Add Kernel metadata for Windows
Add OS version numbers in SORTORDER computation

The SORTORDER is computed like this: ODDHHLL
O: OS type
D: Distribution
H: Version high
L: Version low
windows: add _update_dword() function in registry

This is a helper function used to remove common code found in
windows: Disable Windows Update before booting

Before booting the Windows VM either to install the VirtIO drivers
or to perform the various system preparation tasks, make sure that
the Windows Update is disabled. If it wakes up it can screw things
up.
windows: Enable Auto Update if not sysprepped

When we cleanup all the changes made before booting the Windows VM, only
revert the /Microsoft/Windows/CurrentVersion/WindowsUpdate/Auto Update'
changes if the image has not been syspreped. Those values get deleted
during Sysprep.