Instead of defining a list member inside.

output is a Output class method and using it in _Progress makes the
code more confusing.

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.

If the text was more lines that the height of the active region in the dialog
the 2 last lines were not displayed.

 * Prefix all private methods with _
 * Write missing docstrings
 * Move all public methods above the private ones
 * Add module docstrings where missing
 * Define source code encodings on all modules

If the image gets registered as public allow anyone to read the
metadata and the md5sum file.

This is a workaround for a progress bar bug, where the system may
stay with the cursor hidden if finish() is not called.

Add progress >= 1.0.2 as install_dependency, since this is the version
that fixed the empty progress bar problem.

Also move it to a separate module.

Logging can be enabled using the -l input option

In the cli output classes this method will clear terminal screen if
the standard output is a terminal.

Also fix various issues. snf-image-creator-dialog is almost ready.
Some `Help' entries are missing.

Also create a new output class (InfoBoxOutput) to be used when
performing syspreps