Allow the user to upload the image to a different container than the
"images" one.

As the documentation of libguestfs states, a separated thread should
be started after mount_local has finished and before mount_local_run,
which is a blocking command, gets started. Till now, we used to start
the thread just before mount_local.

Also change the mount() method to be able to use it standalone without
a with statement.

Export the image metadata as environment variables before running
scripts on the mounted image. This way the metadata will be visible
and can be used by the scripts if needed.

Allow the user to change the destination container when uploading
images.

This option can be used to prefix each output line with a timestamp.

If the user specifies /dev/null as output file, omit dumping the image.
This can be used for debug reasons.

Update the image properties accordingly if this is the case

Bump version to 0.9next

Increase the default boot and the shutdown timeout in windows to 10 and
5 minutes respectfully.

Prior to this, if you tried to install the same version of the VirtIO
drivers that where already installed on a Windows media, you would end
up just uninstalling the old ones. This happened because
snf-image-creator added code for installing the new drivers and then for
removing the old ones. Windows would ignore the first request, since the
drivers were already present in the database, but would perform the
second one.

This fixes #44

Fix a typo that raised an AttributeError exception when the input media
was a *BSD system.

Also update the year in the "Copyright" section

This task was added in snf-image v0.18

Check if the deployment task list is empty. If this is the case, a
message should be printed to the user. If we try to initialize the
dialog menu with an empty choices list, the program will crash.

Use a function to determine if a CONFIGURATION_TASK entry specifies
a task that is applicable for the current image's OS type.

An OS was characterized as unknown if the distro was unknown even though
the osfamily was not unknown.

Add the new powerbtn_action sysprep command that controls the action
made when the power button gets pressed.

Workaround the bug that libguestfs may raise a RuntimeError even if the
command runs successfully, due to the fact that the command exited with
non-zero exit status.

Initialize the output modules in the beginning. Let the output instance
print the error message if a Fatal Error occurs.

If --syslog option is passed to snf-mkimage or snf-image-creator, the
program will log its output to syslog too.

This resolves #42

This is only needed for the info method. There is no reason to pollute
the rest of the methods with this.

It is better to create warnings that RuntimeError exceptions.

Make sure to check all the file paths before opening files to collect
metadata. The metadata collecting process takes place in the beginning
and the user cannot control it. Warn if something is missing but do not
throw exceptions

By default add a 10 second boot menu timeout. The user may change
this by altering the bootmenu_timeout sysprep parameter. This works
for GRUB1, GRUB2 and syslinux.

This resolves #41

The function would raise an exception if the value was not a list

Extend the use-persistent-block-device-names sysprep to include support
for the syslinux configuration file (/boot/syslinux.cfg).

This resolves #40