Bump version to 0.7.1next

Bug fixes and documentation updates

Do not search for specific words in it. The messages may be in a
language other than English. Focus on the Numbers.

Do not use format=raw in the -drive option of KVM when booting the
Windows VM. The format could also be qcow2 if the original input media
is a regular file.

Populate this section with instructions on how to troubleshoot
libguestfs's launch failures.

Detect Kubuntu, Lubuntu and Xubuntu

 * Add instructions for CentOS 7
 * Use curl in favor of wget on Fedora and CentOS systems.

When bundling a host, make sure that the UUIDs and the Labels of the
original file systems are preserved.

Bump version to 0.7next

Fix a bug in host-bundling operation were in some cases the computed
new image size was wrong.

Older versions of qemu-img do not accept a '--output json' option

The printed name of the sysprep tasks is constructed from the method
name by replacing the _ with " ". This can be used to overwrite it.

If you print the snapshotting message before disk.file is referenced,
you may end up outputting messages like this:

Snapshotting media source ... Examining source media `<image_file>' ...

Instead of:

Examining source media `<image_file>' ... looks like a block device
Snapshotting media source ... done

If you are a regular user, some root commands like modprobe may not be
in your path.

This exception does not exist in python 2.x

Start by waiting for 5sec before retrying and double the interval
after each retry.

The original value was 5min but was rather small. In Desktop versions
of windows the VirtIO installation may take longer.

When the button is pressed it displays further information about an
installed VirtIO driver.

Feature image format support

Make sure the guestfs VM is killed before we launch the VM that
installs the VirtIO drivers.

snf-image-creator can work with different image formats nowadays.

Only use the device mapper when snapshotting block devices. If the
input media is a regular file, then create a qcow2 image and define
the original media as backing_file.

Use qemu-nbd to export a QEMU image as raw where needed

This used to be a class in the util module, but since this is only used
on the Image, it suits better there.

When snapshotting make sure that the size of the underlying block
device is equal to the input media's virtual size. If the input media
is not raw, the QEMU image driver may grow the underlying image. The
block device should be big enough to allow this kind of operations.

This can be used to act on the original media instead of a device-mapper
snapshot.

This resolves #10

There is no need to associate a loop device with the input media if we
are not snapshotting the input media. The loop device is only needed in
order to use the media with the device-mapper.

If a command needs root privileges use # as prompt. In any other case
use $.

Add a section on how to use snf-image-creator on non-raw format images

If qemu catches a signal, it terminates with 0 and prints a message in
stderr. Try to detect if the process has been terminated by a signal
by examining the stderr.