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

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.

This displays the registration info as returned by ./kamaki and gives
the user the option to save it in a file.

By default the output goes to sys.stdout. This is used in snf-mkimage
to output the plankton answer when registering an image to a synnefo
deployment.

This resolves #21

The base class is named Output. Having a method with the same makes
the code confusing.

This can be used to display the current execution log.

Instead of defining a list member inside.

The type for those parameters is list:<type>

Only use the mount feature in the Image class if it is supported by
the libguestfs build. The feature of mounting an image locally through
FUSE was added in libguestfs 1.18.

Mount the image on the host system using FUSE and libguestfs.

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

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

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 the user picks a directory that contains VirtIO drivers, show him
the version of the discovered drivers in the confirmation box.

Don't treat shrink as a seperated task. Add it in the syspreps menu.

Change the sysprep enabling and disabling mechanism to always work
correct. The previous implementation was buggy and would erroneously
"remember" the executed syspreps on a reset.

 * Cleanup Wizard and WizardPage classes in dialog_wizard
 * Fix various pylint warnings

Add a page in the dialog wizard that displays the current state of
the VirtIO drivers of the image and allow the user to update the
installed VirtIO drivers. This page will only be shown if the media
hosts a Windows image.

The sysprep parameters with the hidden attribute enabled are not
displayed to the user.

Merge the Parameter menu entry with Sysprep and add a new entry for
installing VirtIO drivers. This will only be visible in Windows.

This parameter points to a directory that hosts virtio drivers for
windows.

 * Use select_file() to update a "file" sysprep param
 * Switch the order of <Details> and <Update> buttons
 * Use the last visited menu entry as default item

Rewrite the mechanism to have better control on the system preparation
parameters. Also change the way the parameters are updated in the UI.

If the needed sysprep parameters had all default values,
snf-image-creator would crash when trying to run the image
customization. This bug could not be triggered from the current os_type
classes.

According to the decision of the GRNET Board of Directors,
switch license to GPLv3.

This commit will be propagated to the release
and master branches based on git flow, and the next
release will be licensed as GPLv3.

When adding a new image property, check if the property already exists
or if it contains invalid characters.

Add functionality for deleting image properties in the "Modify"
menu entry in expert mode and completely remove the "Delete" entry.

When we wrap text to create a paragraph and print it in a dialog box,
make sure the lines will not get wrapped further by the dialog box.

This allows us to add a Description field in register. This can be
used to update the DESCRIPTION image property