Allow the characters that kamaki allows

In the documentation and the printed messages, remove all references
to ~okeanos, pithos or cyclades.

 * Change the authentication everywhere to use clouds
   (authentication URL and token pairs)
 * Add menu entries to manage clouds
 * Add an extra -a option in snf-image-creator to allow the user to
   specify authentication URLs

 * 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.

Before uploading to pithos, check if any remote file gets
overwritten.

In kamaki 0.8 `store' command is replaced with `file' and `astakos' is
replaced with `user'.

Support images that can only be deployed by the user that registers
the image to cyclades

You don't need the account name. You can fetch it from astakos using
the authentication token.

It has changed after the last major revision and was not updated.

If present in the kamaki configuration file, the user will read
the ~okeanos credentials using the kamaki config interface.
Whenever the user changes the ~okeanos credentians, the changes are
pushed back to kamaki.

Fixed many `E127 continuation line over-indented for visual indent'
errors

Otherwise the registration may fail.

Let the application decide what to do with them. If image-creator
receives an error from kamaki it will terminate. But this may not be
the proper thing to do for an interactive application like
image-creator-dialog

The progress bar of the progress generator had a wrong max attribute.

All image-creator components now output messages using an instance
of one of the output classes.

Also rearrange input options

This is just a template. Not fully workable

Also merge data_cleanup tasks with syspreps and did a major cleanup

All modules should use image_creator.FatalError exception to report
fatal errors.

* Add foreach_file function in OSBase. This is used by all cleanup
  methods
* Add slackware class. This class derives from linux and overwrites the
  log cleanup behaviour. This is needed since slackware stores all
  package management info in /var/log/packages
* Add a shrink method in DiskDevice. This method shrinks the last
  filesystem to the minimum size
* Make the code style comply with pep8